1 /* SPDX-License-Identifier: GPL-2.0
2 *
3 * IO cost model based controller.
4 *
5 * Copyright (C) 2019 Tejun Heo <tj@kernel.org>
6 * Copyright (C) 2019 Andy Newell <newella@fb.com>
7 * Copyright (C) 2019 Facebook
8 *
9 * One challenge of controlling IO resources is the lack of trivially
10 * observable cost metric. This is distinguished from CPU and memory where
11 * wallclock time and the number of bytes can serve as accurate enough
12 * approximations.
13 *
14 * Bandwidth and iops are the most commonly used metrics for IO devices but
15 * depending on the type and specifics of the device, different IO patterns
16 * easily lead to multiple orders of magnitude variations rendering them
17 * useless for the purpose of IO capacity distribution. While on-device
18 * time, with a lot of clutches, could serve as a useful approximation for
19 * non-queued rotational devices, this is no longer viable with modern
20 * devices, even the rotational ones.
21 *
22 * While there is no cost metric we can trivially observe, it isn't a
23 * complete mystery. For example, on a rotational device, seek cost
24 * dominates while a contiguous transfer contributes a smaller amount
25 * proportional to the size. If we can characterize at least the relative
26 * costs of these different types of IOs, it should be possible to
27 * implement a reasonable work-conserving proportional IO resource
28 * distribution.
29 *
30 * 1. IO Cost Model
31 *
32 * IO cost model estimates the cost of an IO given its basic parameters and
33 * history (e.g. the end sector of the last IO). The cost is measured in
34 * device time. If a given IO is estimated to cost 10ms, the device should
35 * be able to process ~100 of those IOs in a second.
36 *
37 * Currently, there's only one builtin cost model - linear. Each IO is
38 * classified as sequential or random and given a base cost accordingly.
39 * On top of that, a size cost proportional to the length of the IO is
40 * added. While simple, this model captures the operational
41 * characteristics of a wide varienty of devices well enough. Default
42 * parameters for several different classes of devices are provided and the
43 * parameters can be configured from userspace via
44 * /sys/fs/cgroup/io.cost.model.
45 *
46 * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate
47 * device-specific coefficients.
48 *
49 * 2. Control Strategy
50 *
51 * The device virtual time (vtime) is used as the primary control metric.
52 * The control strategy is composed of the following three parts.
53 *
54 * 2-1. Vtime Distribution
55 *
56 * When a cgroup becomes active in terms of IOs, its hierarchical share is
57 * calculated. Please consider the following hierarchy where the numbers
58 * inside parentheses denote the configured weights.
59 *
60 * root
61 * / \
62 * A (w:100) B (w:300)
63 * / \
64 * A0 (w:100) A1 (w:100)
65 *
66 * If B is idle and only A0 and A1 are actively issuing IOs, as the two are
67 * of equal weight, each gets 50% share. If then B starts issuing IOs, B
68 * gets 300/(100+300) or 75% share, and A0 and A1 equally splits the rest,
69 * 12.5% each. The distribution mechanism only cares about these flattened
70 * shares. They're called hweights (hierarchical weights) and always add
71 * upto 1 (WEIGHT_ONE).
72 *
73 * A given cgroup's vtime runs slower in inverse proportion to its hweight.
74 * For example, with 12.5% weight, A0's time runs 8 times slower (100/12.5)
75 * against the device vtime - an IO which takes 10ms on the underlying
76 * device is considered to take 80ms on A0.
77 *
78 * This constitutes the basis of IO capacity distribution. Each cgroup's
79 * vtime is running at a rate determined by its hweight. A cgroup tracks
80 * the vtime consumed by past IOs and can issue a new IO if doing so
81 * wouldn't outrun the current device vtime. Otherwise, the IO is
82 * suspended until the vtime has progressed enough to cover it.
83 *
84 * 2-2. Vrate Adjustment
85 *
86 * It's unrealistic to expect the cost model to be perfect. There are too
87 * many devices and even on the same device the overall performance
88 * fluctuates depending on numerous factors such as IO mixture and device
89 * internal garbage collection. The controller needs to adapt dynamically.
90 *
91 * This is achieved by adjusting the overall IO rate according to how busy
92 * the device is. If the device becomes overloaded, we're sending down too
93 * many IOs and should generally slow down. If there are waiting issuers
94 * but the device isn't saturated, we're issuing too few and should
95 * generally speed up.
96 *
97 * To slow down, we lower the vrate - the rate at which the device vtime
98 * passes compared to the wall clock. For example, if the vtime is running
99 * at the vrate of 75%, all cgroups added up would only be able to issue
100 * 750ms worth of IOs per second, and vice-versa for speeding up.
101 *
102 * Device business is determined using two criteria - rq wait and
103 * completion latencies.
104 *
105 * When a device gets saturated, the on-device and then the request queues
106 * fill up and a bio which is ready to be issued has to wait for a request
107 * to become available. When this delay becomes noticeable, it's a clear
108 * indication that the device is saturated and we lower the vrate. This
109 * saturation signal is fairly conservative as it only triggers when both
110 * hardware and software queues are filled up, and is used as the default
111 * busy signal.
112 *
113 * As devices can have deep queues and be unfair in how the queued commands
114 * are executed, solely depending on rq wait may not result in satisfactory
115 * control quality. For a better control quality, completion latency QoS
116 * parameters can be configured so that the device is considered saturated
117 * if N'th percentile completion latency rises above the set point.
118 *
119 * The completion latency requirements are a function of both the
120 * underlying device characteristics and the desired IO latency quality of
121 * service. There is an inherent trade-off - the tighter the latency QoS,
122 * the higher the bandwidth lossage. Latency QoS is disabled by default
123 * and can be set through /sys/fs/cgroup/io.cost.qos.
124 *
125 * 2-3. Work Conservation
126 *
127 * Imagine two cgroups A and B with equal weights. A is issuing a small IO
128 * periodically while B is sending out enough parallel IOs to saturate the
129 * device on its own. Let's say A's usage amounts to 100ms worth of IO
130 * cost per second, i.e., 10% of the device capacity. The naive
131 * distribution of half and half would lead to 60% utilization of the
132 * device, a significant reduction in the total amount of work done
133 * compared to free-for-all competition. This is too high a cost to pay
134 * for IO control.
135 *
136 * To conserve the total amount of work done, we keep track of how much
137 * each active cgroup is actually using and yield part of its weight if
138 * there are other cgroups which can make use of it. In the above case,
139 * A's weight will be lowered so that it hovers above the actual usage and
140 * B would be able to use the rest.
141 *
142 * As we don't want to penalize a cgroup for donating its weight, the
143 * surplus weight adjustment factors in a margin and has an immediate
144 * snapback mechanism in case the cgroup needs more IO vtime for itself.
145 *
146 * Note that adjusting down surplus weights has the same effects as
147 * accelerating vtime for other cgroups and work conservation can also be
148 * implemented by adjusting vrate dynamically. However, squaring who can
149 * donate and should take back how much requires hweight propagations
150 * anyway making it easier to implement and understand as a separate
151 * mechanism.
152 *
153 * 3. Monitoring
154 *
155 * Instead of debugfs or other clumsy monitoring mechanisms, this
156 * controller uses a drgn based monitoring script -
157 * tools/cgroup/iocost_monitor.py. For details on drgn, please see
158 * https://github.com/osandov/drgn. The output looks like the following.
159 *
160 * sdb RUN per=300ms cur_per=234.218:v203.695 busy= +1 vrate= 62.12%
161 * active weight hweight% inflt% dbt delay usages%
162 * test/a * 50/ 50 33.33/ 33.33 27.65 2 0*041 033:033:033
163 * test/b * 100/ 100 66.67/ 66.67 17.56 0 0*000 066:079:077
164 *
165 * - per : Timer period
166 * - cur_per : Internal wall and device vtime clock
167 * - vrate : Device virtual time rate against wall clock
168 * - weight : Surplus-adjusted and configured weights
169 * - hweight : Surplus-adjusted and configured hierarchical weights
170 * - inflt : The percentage of in-flight IO cost at the end of last period
171 * - del_ms : Deferred issuer delay induction level and duration
172 * - usages : Usage history
173 */
174
175 #include <linux/kernel.h>
176 #include <linux/module.h>
177 #include <linux/timer.h>
178 #include <linux/time64.h>
179 #include <linux/parser.h>
180 #include <linux/sched/signal.h>
181 #include <asm/local.h>
182 #include <asm/local64.h>
183 #include "blk-rq-qos.h"
184 #include "blk-stat.h"
185 #include "blk-wbt.h"
186 #include "blk-cgroup.h"
187
188 #ifdef CONFIG_TRACEPOINTS
189
190 /* copied from TRACE_CGROUP_PATH, see cgroup-internal.h */
191 #define TRACE_IOCG_PATH_LEN 1024
192 static DEFINE_SPINLOCK(trace_iocg_path_lock);
193 static char trace_iocg_path[TRACE_IOCG_PATH_LEN];
194
195 #define TRACE_IOCG_PATH(type, iocg, ...) \
196 do { \
197 unsigned long flags; \
198 if (trace_iocost_##type##_enabled()) { \
199 spin_lock_irqsave(&trace_iocg_path_lock, flags); \
200 cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup, \
201 trace_iocg_path, TRACE_IOCG_PATH_LEN); \
202 trace_iocost_##type(iocg, trace_iocg_path, \
203 ##__VA_ARGS__); \
204 spin_unlock_irqrestore(&trace_iocg_path_lock, flags); \
205 } \
206 } while (0)
207
208 #else /* CONFIG_TRACE_POINTS */
209 #define TRACE_IOCG_PATH(type, iocg, ...) do { } while (0)
210 #endif /* CONFIG_TRACE_POINTS */
211
212 enum {
213 MILLION = 1000000,
214
215 /* timer period is calculated from latency requirements, bound it */
216 MIN_PERIOD = USEC_PER_MSEC,
217 MAX_PERIOD = USEC_PER_SEC,
218
219 /*
220 * iocg->vtime is targeted at 50% behind the device vtime, which
221 * serves as its IO credit buffer. Surplus weight adjustment is
222 * immediately canceled if the vtime margin runs below 10%.
223 */
224 MARGIN_MIN_PCT = 10,
225 MARGIN_LOW_PCT = 20,
226 MARGIN_TARGET_PCT = 50,
227
228 INUSE_ADJ_STEP_PCT = 25,
229
230 /* Have some play in timer operations */
231 TIMER_SLACK_PCT = 1,
232
233 /* 1/64k is granular enough and can easily be handled w/ u32 */
234 WEIGHT_ONE = 1 << 16,
235 };
236
237 enum {
238 /*
239 * As vtime is used to calculate the cost of each IO, it needs to
240 * be fairly high precision. For example, it should be able to
241 * represent the cost of a single page worth of discard with
242 * suffificient accuracy. At the same time, it should be able to
243 * represent reasonably long enough durations to be useful and
244 * convenient during operation.
245 *
246 * 1s worth of vtime is 2^37. This gives us both sub-nanosecond
247 * granularity and days of wrap-around time even at extreme vrates.
248 */
249 VTIME_PER_SEC_SHIFT = 37,
250 VTIME_PER_SEC = 1LLU << VTIME_PER_SEC_SHIFT,
251 VTIME_PER_USEC = VTIME_PER_SEC / USEC_PER_SEC,
252 VTIME_PER_NSEC = VTIME_PER_SEC / NSEC_PER_SEC,
253
254 /* bound vrate adjustments within two orders of magnitude */
255 VRATE_MIN_PPM = 10000, /* 1% */
256 VRATE_MAX_PPM = 100000000, /* 10000% */
257
258 VRATE_MIN = VTIME_PER_USEC * VRATE_MIN_PPM / MILLION,
259 VRATE_CLAMP_ADJ_PCT = 4,
260
261 /* switch iff the conditions are met for longer than this */
262 AUTOP_CYCLE_NSEC = 10LLU * NSEC_PER_SEC,
263 };
264
265 enum {
266 /* if IOs end up waiting for requests, issue less */
267 RQ_WAIT_BUSY_PCT = 5,
268
269 /* unbusy hysterisis */
270 UNBUSY_THR_PCT = 75,
271
272 /*
273 * The effect of delay is indirect and non-linear and a huge amount of
274 * future debt can accumulate abruptly while unthrottled. Linearly scale
275 * up delay as debt is going up and then let it decay exponentially.
276 * This gives us quick ramp ups while delay is accumulating and long
277 * tails which can help reducing the frequency of debt explosions on
278 * unthrottle. The parameters are experimentally determined.
279 *
280 * The delay mechanism provides adequate protection and behavior in many
281 * cases. However, this is far from ideal and falls shorts on both
282 * fronts. The debtors are often throttled too harshly costing a
283 * significant level of fairness and possibly total work while the
284 * protection against their impacts on the system can be choppy and
285 * unreliable.
286 *
287 * The shortcoming primarily stems from the fact that, unlike for page
288 * cache, the kernel doesn't have well-defined back-pressure propagation
289 * mechanism and policies for anonymous memory. Fully addressing this
290 * issue will likely require substantial improvements in the area.
291 */
292 MIN_DELAY_THR_PCT = 500,
293 MAX_DELAY_THR_PCT = 25000,
294 MIN_DELAY = 250,
295 MAX_DELAY = 250 * USEC_PER_MSEC,
296
297 /* halve debts if avg usage over 100ms is under 50% */
298 DFGV_USAGE_PCT = 50,
299 DFGV_PERIOD = 100 * USEC_PER_MSEC,
300
301 /* don't let cmds which take a very long time pin lagging for too long */
302 MAX_LAGGING_PERIODS = 10,
303
304 /*
305 * Count IO size in 4k pages. The 12bit shift helps keeping
306 * size-proportional components of cost calculation in closer
307 * numbers of digits to per-IO cost components.
308 */
309 IOC_PAGE_SHIFT = 12,
310 IOC_PAGE_SIZE = 1 << IOC_PAGE_SHIFT,
311 IOC_SECT_TO_PAGE_SHIFT = IOC_PAGE_SHIFT - SECTOR_SHIFT,
312
313 /* if apart further than 16M, consider randio for linear model */
314 LCOEF_RANDIO_PAGES = 4096,
315 };
316
317 enum ioc_running {
318 IOC_IDLE,
319 IOC_RUNNING,
320 IOC_STOP,
321 };
322
323 /* io.cost.qos controls including per-dev enable of the whole controller */
324 enum {
325 QOS_ENABLE,
326 QOS_CTRL,
327 NR_QOS_CTRL_PARAMS,
328 };
329
330 /* io.cost.qos params */
331 enum {
332 QOS_RPPM,
333 QOS_RLAT,
334 QOS_WPPM,
335 QOS_WLAT,
336 QOS_MIN,
337 QOS_MAX,
338 NR_QOS_PARAMS,
339 };
340
341 /* io.cost.model controls */
342 enum {
343 COST_CTRL,
344 COST_MODEL,
345 NR_COST_CTRL_PARAMS,
346 };
347
348 /* builtin linear cost model coefficients */
349 enum {
350 I_LCOEF_RBPS,
351 I_LCOEF_RSEQIOPS,
352 I_LCOEF_RRANDIOPS,
353 I_LCOEF_WBPS,
354 I_LCOEF_WSEQIOPS,
355 I_LCOEF_WRANDIOPS,
356 NR_I_LCOEFS,
357 };
358
359 enum {
360 LCOEF_RPAGE,
361 LCOEF_RSEQIO,
362 LCOEF_RRANDIO,
363 LCOEF_WPAGE,
364 LCOEF_WSEQIO,
365 LCOEF_WRANDIO,
366 NR_LCOEFS,
367 };
368
369 enum {
370 AUTOP_INVALID,
371 AUTOP_HDD,
372 AUTOP_SSD_QD1,
373 AUTOP_SSD_DFL,
374 AUTOP_SSD_FAST,
375 };
376
377 struct ioc_params {
378 u32 qos[NR_QOS_PARAMS];
379 u64 i_lcoefs[NR_I_LCOEFS];
380 u64 lcoefs[NR_LCOEFS];
381 u32 too_fast_vrate_pct;
382 u32 too_slow_vrate_pct;
383 };
384
385 struct ioc_margins {
386 s64 min;
387 s64 low;
388 s64 target;
389 };
390
391 struct ioc_missed {
392 local_t nr_met;
393 local_t nr_missed;
394 u32 last_met;
395 u32 last_missed;
396 };
397
398 struct ioc_pcpu_stat {
399 struct ioc_missed missed[2];
400
401 local64_t rq_wait_ns;
402 u64 last_rq_wait_ns;
403 };
404
405 /* per device */
406 struct ioc {
407 struct rq_qos rqos;
408
409 bool enabled;
410
411 struct ioc_params params;
412 struct ioc_margins margins;
413 u32 period_us;
414 u32 timer_slack_ns;
415 u64 vrate_min;
416 u64 vrate_max;
417
418 spinlock_t lock;
419 struct timer_list timer;
420 struct list_head active_iocgs; /* active cgroups */
421 struct ioc_pcpu_stat __percpu *pcpu_stat;
422
423 enum ioc_running running;
424 atomic64_t vtime_rate;
425 u64 vtime_base_rate;
426 s64 vtime_err;
427
428 seqcount_spinlock_t period_seqcount;
429 u64 period_at; /* wallclock starttime */
430 u64 period_at_vtime; /* vtime starttime */
431
432 atomic64_t cur_period; /* inc'd each period */
433 int busy_level; /* saturation history */
434
435 bool weights_updated;
436 atomic_t hweight_gen; /* for lazy hweights */
437
438 /* debt forgivness */
439 u64 dfgv_period_at;
440 u64 dfgv_period_rem;
441 u64 dfgv_usage_us_sum;
442
443 u64 autop_too_fast_at;
444 u64 autop_too_slow_at;
445 int autop_idx;
446 bool user_qos_params:1;
447 bool user_cost_model:1;
448 };
449
450 struct iocg_pcpu_stat {
451 local64_t abs_vusage;
452 };
453
454 struct iocg_stat {
455 u64 usage_us;
456 u64 wait_us;
457 u64 indebt_us;
458 u64 indelay_us;
459 };
460
461 /* per device-cgroup pair */
462 struct ioc_gq {
463 struct blkg_policy_data pd;
464 struct ioc *ioc;
465
466 /*
467 * A iocg can get its weight from two sources - an explicit
468 * per-device-cgroup configuration or the default weight of the
469 * cgroup. `cfg_weight` is the explicit per-device-cgroup
470 * configuration. `weight` is the effective considering both
471 * sources.
472 *
473 * When an idle cgroup becomes active its `active` goes from 0 to
474 * `weight`. `inuse` is the surplus adjusted active weight.
475 * `active` and `inuse` are used to calculate `hweight_active` and
476 * `hweight_inuse`.
477 *
478 * `last_inuse` remembers `inuse` while an iocg is idle to persist
479 * surplus adjustments.
480 *
481 * `inuse` may be adjusted dynamically during period. `saved_*` are used
482 * to determine and track adjustments.
483 */
484 u32 cfg_weight;
485 u32 weight;
486 u32 active;
487 u32 inuse;
488
489 u32 last_inuse;
490 s64 saved_margin;
491
492 sector_t cursor; /* to detect randio */
493
494 /*
495 * `vtime` is this iocg's vtime cursor which progresses as IOs are
496 * issued. If lagging behind device vtime, the delta represents
497 * the currently available IO budget. If running ahead, the
498 * overage.
499 *
500 * `vtime_done` is the same but progressed on completion rather
501 * than issue. The delta behind `vtime` represents the cost of
502 * currently in-flight IOs.
503 */
504 atomic64_t vtime;
505 atomic64_t done_vtime;
506 u64 abs_vdebt;
507
508 /* current delay in effect and when it started */
509 u64 delay;
510 u64 delay_at;
511
512 /*
513 * The period this iocg was last active in. Used for deactivation
514 * and invalidating `vtime`.
515 */
516 atomic64_t active_period;
517 struct list_head active_list;
518
519 /* see __propagate_weights() and current_hweight() for details */
520 u64 child_active_sum;
521 u64 child_inuse_sum;
522 u64 child_adjusted_sum;
523 int hweight_gen;
524 u32 hweight_active;
525 u32 hweight_inuse;
526 u32 hweight_donating;
527 u32 hweight_after_donation;
528
529 struct list_head walk_list;
530 struct list_head surplus_list;
531
532 struct wait_queue_head waitq;
533 struct hrtimer waitq_timer;
534
535 /* timestamp at the latest activation */
536 u64 activated_at;
537
538 /* statistics */
539 struct iocg_pcpu_stat __percpu *pcpu_stat;
540 struct iocg_stat stat;
541 struct iocg_stat last_stat;
542 u64 last_stat_abs_vusage;
543 u64 usage_delta_us;
544 u64 wait_since;
545 u64 indebt_since;
546 u64 indelay_since;
547
548 /* this iocg's depth in the hierarchy and ancestors including self */
549 int level;
550 struct ioc_gq *ancestors[];
551 };
552
553 /* per cgroup */
554 struct ioc_cgrp {
555 struct blkcg_policy_data cpd;
556 unsigned int dfl_weight;
557 };
558
559 struct ioc_now {
560 u64 now_ns;
561 u64 now;
562 u64 vnow;
563 };
564
565 struct iocg_wait {
566 struct wait_queue_entry wait;
567 struct bio *bio;
568 u64 abs_cost;
569 bool committed;
570 };
571
572 struct iocg_wake_ctx {
573 struct ioc_gq *iocg;
574 u32 hw_inuse;
575 s64 vbudget;
576 };
577
578 static const struct ioc_params autop[] = {
579 [AUTOP_HDD] = {
580 .qos = {
581 [QOS_RLAT] = 250000, /* 250ms */
582 [QOS_WLAT] = 250000,
583 [QOS_MIN] = VRATE_MIN_PPM,
584 [QOS_MAX] = VRATE_MAX_PPM,
585 },
586 .i_lcoefs = {
587 [I_LCOEF_RBPS] = 174019176,
588 [I_LCOEF_RSEQIOPS] = 41708,
589 [I_LCOEF_RRANDIOPS] = 370,
590 [I_LCOEF_WBPS] = 178075866,
591 [I_LCOEF_WSEQIOPS] = 42705,
592 [I_LCOEF_WRANDIOPS] = 378,
593 },
594 },
595 [AUTOP_SSD_QD1] = {
596 .qos = {
597 [QOS_RLAT] = 25000, /* 25ms */
598 [QOS_WLAT] = 25000,
599 [QOS_MIN] = VRATE_MIN_PPM,
600 [QOS_MAX] = VRATE_MAX_PPM,
601 },
602 .i_lcoefs = {
603 [I_LCOEF_RBPS] = 245855193,
604 [I_LCOEF_RSEQIOPS] = 61575,
605 [I_LCOEF_RRANDIOPS] = 6946,
606 [I_LCOEF_WBPS] = 141365009,
607 [I_LCOEF_WSEQIOPS] = 33716,
608 [I_LCOEF_WRANDIOPS] = 26796,
609 },
610 },
611 [AUTOP_SSD_DFL] = {
612 .qos = {
613 [QOS_RLAT] = 25000, /* 25ms */
614 [QOS_WLAT] = 25000,
615 [QOS_MIN] = VRATE_MIN_PPM,
616 [QOS_MAX] = VRATE_MAX_PPM,
617 },
618 .i_lcoefs = {
619 [I_LCOEF_RBPS] = 488636629,
620 [I_LCOEF_RSEQIOPS] = 8932,
621 [I_LCOEF_RRANDIOPS] = 8518,
622 [I_LCOEF_WBPS] = 427891549,
623 [I_LCOEF_WSEQIOPS] = 28755,
624 [I_LCOEF_WRANDIOPS] = 21940,
625 },
626 .too_fast_vrate_pct = 500,
627 },
628 [AUTOP_SSD_FAST] = {
629 .qos = {
630 [QOS_RLAT] = 5000, /* 5ms */
631 [QOS_WLAT] = 5000,
632 [QOS_MIN] = VRATE_MIN_PPM,
633 [QOS_MAX] = VRATE_MAX_PPM,
634 },
635 .i_lcoefs = {
636 [I_LCOEF_RBPS] = 3102524156LLU,
637 [I_LCOEF_RSEQIOPS] = 724816,
638 [I_LCOEF_RRANDIOPS] = 778122,
639 [I_LCOEF_WBPS] = 1742780862LLU,
640 [I_LCOEF_WSEQIOPS] = 425702,
641 [I_LCOEF_WRANDIOPS] = 443193,
642 },
643 .too_slow_vrate_pct = 10,
644 },
645 };
646
647 /*
648 * vrate adjust percentages indexed by ioc->busy_level. We adjust up on
649 * vtime credit shortage and down on device saturation.
650 */
651 static u32 vrate_adj_pct[] =
652 { 0, 0, 0, 0,
653 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
654 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
655 4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16 };
656
657 static struct blkcg_policy blkcg_policy_iocost;
658
659 /* accessors and helpers */
660 static struct ioc *rqos_to_ioc(struct rq_qos *rqos)
661 {
662 return container_of(rqos, struct ioc, rqos);
663 }
664
665 static struct ioc *q_to_ioc(struct request_queue *q)
666 {
667 return rqos_to_ioc(rq_qos_id(q, RQ_QOS_COST));
668 }
669
670 static const char __maybe_unused *ioc_name(struct ioc *ioc)
671 {
672 struct gendisk *disk = ioc->rqos.disk;
673
674 if (!disk)
675 return "<unknown>";
676 return disk->disk_name;
677 }
678
679 static struct ioc_gq *pd_to_iocg(struct blkg_policy_data *pd)
680 {
681 return pd ? container_of(pd, struct ioc_gq, pd) : NULL;
682 }
683
684 static struct ioc_gq *blkg_to_iocg(struct blkcg_gq *blkg)
685 {
686 return pd_to_iocg(blkg_to_pd(blkg, &blkcg_policy_iocost));
687 }
688
689 static struct blkcg_gq *iocg_to_blkg(struct ioc_gq *iocg)
690 {
691 return pd_to_blkg(&iocg->pd);
692 }
693
694 static struct ioc_cgrp *blkcg_to_iocc(struct blkcg *blkcg)
695 {
696 return container_of(blkcg_to_cpd(blkcg, &blkcg_policy_iocost),
697 struct ioc_cgrp, cpd);
698 }
699
700 /*
701 * Scale @abs_cost to the inverse of @hw_inuse. The lower the hierarchical
702 * weight, the more expensive each IO. Must round up.
703 */
704 static u64 abs_cost_to_cost(u64 abs_cost, u32 hw_inuse)
705 {
706 return DIV64_U64_ROUND_UP(abs_cost * WEIGHT_ONE, hw_inuse);
707 }
708
709 /*
710 * The inverse of abs_cost_to_cost(). Must round up.
711 */
712 static u64 cost_to_abs_cost(u64 cost, u32 hw_inuse)
713 {
714 return DIV64_U64_ROUND_UP(cost * hw_inuse, WEIGHT_ONE);
715 }
716
717 static void iocg_commit_bio(struct ioc_gq *iocg, struct bio *bio,
718 u64 abs_cost, u64 cost)
719 {
720 struct iocg_pcpu_stat *gcs;
721
722 bio->bi_iocost_cost = cost;
723 atomic64_add(cost, &iocg->vtime);
724
725 gcs = get_cpu_ptr(iocg->pcpu_stat);
726 local64_add(abs_cost, &gcs->abs_vusage);
727 put_cpu_ptr(gcs);
728 }
729
730 static void iocg_lock(struct ioc_gq *iocg, bool lock_ioc, unsigned long *flags)
731 {
732 if (lock_ioc) {
733 spin_lock_irqsave(&iocg->ioc->lock, *flags);
734 spin_lock(&iocg->waitq.lock);
735 } else {
736 spin_lock_irqsave(&iocg->waitq.lock, *flags);
737 }
738 }
739
740 static void iocg_unlock(struct ioc_gq *iocg, bool unlock_ioc, unsigned long *flags)
741 {
742 if (unlock_ioc) {
743 spin_unlock(&iocg->waitq.lock);
744 spin_unlock_irqrestore(&iocg->ioc->lock, *flags);
745 } else {
746 spin_unlock_irqrestore(&iocg->waitq.lock, *flags);
747 }
748 }
749
750 #define CREATE_TRACE_POINTS
751 #include <trace/events/iocost.h>
752
753 static void ioc_refresh_margins(struct ioc *ioc)
754 {
755 struct ioc_margins *margins = &ioc->margins;
756 u32 period_us = ioc->period_us;
757 u64 vrate = ioc->vtime_base_rate;
758
759 margins->min = (period_us * MARGIN_MIN_PCT / 100) * vrate;
760 margins->low = (period_us * MARGIN_LOW_PCT / 100) * vrate;
761 margins->target = (period_us * MARGIN_TARGET_PCT / 100) * vrate;
762 }
763
764 /* latency Qos params changed, update period_us and all the dependent params */
765 static void ioc_refresh_period_us(struct ioc *ioc)
766 {
767 u32 ppm, lat, multi, period_us;
768
769 lockdep_assert_held(&ioc->lock);
770
771 /* pick the higher latency target */
772 if (ioc->params.qos[QOS_RLAT] >= ioc->params.qos[QOS_WLAT]) {
773 ppm = ioc->params.qos[QOS_RPPM];
774 lat = ioc->params.qos[QOS_RLAT];
775 } else {
776 ppm = ioc->params.qos[QOS_WPPM];
777 lat = ioc->params.qos[QOS_WLAT];
778 }
779
780 /*
781 * We want the period to be long enough to contain a healthy number
782 * of IOs while short enough for granular control. Define it as a
783 * multiple of the latency target. Ideally, the multiplier should
784 * be scaled according to the percentile so that it would nominally
785 * contain a certain number of requests. Let's be simpler and
786 * scale it linearly so that it's 2x >= pct(90) and 10x at pct(50).
787 */
788 if (ppm)
789 multi = max_t(u32, (MILLION - ppm) / 50000, 2);
790 else
791 multi = 2;
792 period_us = multi * lat;
793 period_us = clamp_t(u32, period_us, MIN_PERIOD, MAX_PERIOD);
794
795 /* calculate dependent params */
796 ioc->period_us = period_us;
797 ioc->timer_slack_ns = div64_u64(
798 (u64)period_us * NSEC_PER_USEC * TIMER_SLACK_PCT,
799 100);
800 ioc_refresh_margins(ioc);
801 }
802
803 /*
804 * ioc->rqos.disk isn't initialized when this function is called from
805 * the init path.
806 */
807 static int ioc_autop_idx(struct ioc *ioc, struct gendisk *disk)
808 {
809 int idx = ioc->autop_idx;
810 const struct ioc_params *p = &autop[idx];
811 u32 vrate_pct;
812 u64 now_ns;
813
814 /* rotational? */
815 if (!blk_queue_nonrot(disk->queue))
816 return AUTOP_HDD;
817
818 /* handle SATA SSDs w/ broken NCQ */
819 if (blk_queue_depth(disk->queue) == 1)
820 return AUTOP_SSD_QD1;
821
822 /* use one of the normal ssd sets */
823 if (idx < AUTOP_SSD_DFL)
824 return AUTOP_SSD_DFL;
825
826 /* if user is overriding anything, maintain what was there */
827 if (ioc->user_qos_params || ioc->user_cost_model)
828 return idx;
829
830 /* step up/down based on the vrate */
831 vrate_pct = div64_u64(ioc->vtime_base_rate * 100, VTIME_PER_USEC);
832 now_ns = blk_time_get_ns();
833
834 if (p->too_fast_vrate_pct && p->too_fast_vrate_pct <= vrate_pct) {
835 if (!ioc->autop_too_fast_at)
836 ioc->autop_too_fast_at = now_ns;
837 if (now_ns - ioc->autop_too_fast_at >= AUTOP_CYCLE_NSEC)
838 return idx + 1;
839 } else {
840 ioc->autop_too_fast_at = 0;
841 }
842
843 if (p->too_slow_vrate_pct && p->too_slow_vrate_pct >= vrate_pct) {
844 if (!ioc->autop_too_slow_at)
845 ioc->autop_too_slow_at = now_ns;
846 if (now_ns - ioc->autop_too_slow_at >= AUTOP_CYCLE_NSEC)
847 return idx - 1;
848 } else {
849 ioc->autop_too_slow_at = 0;
850 }
851
852 return idx;
853 }
854
855 /*
856 * Take the followings as input
857 *
858 * @bps maximum sequential throughput
859 * @seqiops maximum sequential 4k iops
860 * @randiops maximum random 4k iops
861 *
862 * and calculate the linear model cost coefficients.
863 *
864 * *@page per-page cost 1s / (@bps / 4096)
865 * *@seqio base cost of a seq IO max((1s / @seqiops) - *@page, 0)
866 * @randiops base cost of a rand IO max((1s / @randiops) - *@page, 0)
867 */
868 static void calc_lcoefs(u64 bps, u64 seqiops, u64 randiops,
869 u64 *page, u64 *seqio, u64 *randio)
870 {
871 u64 v;
872
873 *page = *seqio = *randio = 0;
874
875 if (bps) {
876 u64 bps_pages = DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE);
877
878 if (bps_pages)
879 *page = DIV64_U64_ROUND_UP(VTIME_PER_SEC, bps_pages);
880 else
881 *page = 1;
882 }
883
884 if (seqiops) {
885 v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops);
886 if (v > *page)
887 *seqio = v - *page;
888 }
889
890 if (randiops) {
891 v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, randiops);
892 if (v > *page)
893 *randio = v - *page;
894 }
895 }
896
897 static void ioc_refresh_lcoefs(struct ioc *ioc)
898 {
899 u64 *u = ioc->params.i_lcoefs;
900 u64 *c = ioc->params.lcoefs;
901
902 calc_lcoefs(u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
903 &c[LCOEF_RPAGE], &c[LCOEF_RSEQIO], &c[LCOEF_RRANDIO]);
904 calc_lcoefs(u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS],
905 &c[LCOEF_WPAGE], &c[LCOEF_WSEQIO], &c[LCOEF_WRANDIO]);
906 }
907
908 /*
909 * struct gendisk is required as an argument because ioc->rqos.disk
910 * is not properly initialized when called from the init path.
911 */
912 static bool ioc_refresh_params_disk(struct ioc *ioc, bool force,
913 struct gendisk *disk)
914 {
915 const struct ioc_params *p;
916 int idx;
917
918 lockdep_assert_held(&ioc->lock);
919
920 idx = ioc_autop_idx(ioc, disk);
921 p = &autop[idx];
922
923 if (idx == ioc->autop_idx && !force)
924 return false;
925
926 if (idx != ioc->autop_idx) {
927 atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);
928 ioc->vtime_base_rate = VTIME_PER_USEC;
929 }
930
931 ioc->autop_idx = idx;
932 ioc->autop_too_fast_at = 0;
933 ioc->autop_too_slow_at = 0;
934
935 if (!ioc->user_qos_params)
936 memcpy(ioc->params.qos, p->qos, sizeof(p->qos));
937 if (!ioc->user_cost_model)
938 memcpy(ioc->params.i_lcoefs, p->i_lcoefs, sizeof(p->i_lcoefs));
939
940 ioc_refresh_period_us(ioc);
941 ioc_refresh_lcoefs(ioc);
942
943 ioc->vrate_min = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MIN] *
944 VTIME_PER_USEC, MILLION);
945 ioc->vrate_max = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MAX] *
946 VTIME_PER_USEC, MILLION);
947
948 return true;
949 }
950
951 static bool ioc_refresh_params(struct ioc *ioc, bool force)
952 {
953 return ioc_refresh_params_disk(ioc, force, ioc->rqos.disk);
954 }
955
956 /*
957 * When an iocg accumulates too much vtime or gets deactivated, we throw away
958 * some vtime, which lowers the overall device utilization. As the exact amount
959 * which is being thrown away is known, we can compensate by accelerating the
960 * vrate accordingly so that the extra vtime generated in the current period
961 * matches what got lost.
962 */
963 static void ioc_refresh_vrate(struct ioc *ioc, struct ioc_now *now)
964 {
965 s64 pleft = ioc->period_at + ioc->period_us - now->now;
966 s64 vperiod = ioc->period_us * ioc->vtime_base_rate;
967 s64 vcomp, vcomp_min, vcomp_max;
968
969 lockdep_assert_held(&ioc->lock);
970
971 /* we need some time left in this period */
972 if (pleft <= 0)
973 goto done;
974
975 /*
976 * Calculate how much vrate should be adjusted to offset the error.
977 * Limit the amount of adjustment and deduct the adjusted amount from
978 * the error.
979 */
980 vcomp = -div64_s64(ioc->vtime_err, pleft);
981 vcomp_min = -(ioc->vtime_base_rate >> 1);
982 vcomp_max = ioc->vtime_base_rate;
983 vcomp = clamp(vcomp, vcomp_min, vcomp_max);
984
985 ioc->vtime_err += vcomp * pleft;
986
987 atomic64_set(&ioc->vtime_rate, ioc->vtime_base_rate + vcomp);
988 done:
989 /* bound how much error can accumulate */
990 ioc->vtime_err = clamp(ioc->vtime_err, -vperiod, vperiod);
991 }
992
993 static void ioc_adjust_base_vrate(struct ioc *ioc, u32 rq_wait_pct,
994 int nr_lagging, int nr_shortages,
995 int prev_busy_level, u32 *missed_ppm)
996 {
997 u64 vrate = ioc->vtime_base_rate;
998 u64 vrate_min = ioc->vrate_min, vrate_max = ioc->vrate_max;
999
1000 if (!ioc->busy_level || (ioc->busy_level < 0 && nr_lagging)) {
1001 if (ioc->busy_level != prev_busy_level || nr_lagging)
1002 trace_iocost_ioc_vrate_adj(ioc, vrate,
1003 missed_ppm, rq_wait_pct,
1004 nr_lagging, nr_shortages);
1005
1006 return;
1007 }
1008
1009 /*
1010 * If vrate is out of bounds, apply clamp gradually as the
1011 * bounds can change abruptly. Otherwise, apply busy_level
1012 * based adjustment.
1013 */
1014 if (vrate < vrate_min) {
1015 vrate = div64_u64(vrate * (100 + VRATE_CLAMP_ADJ_PCT), 100);
1016 vrate = min(vrate, vrate_min);
1017 } else if (vrate > vrate_max) {
1018 vrate = div64_u64(vrate * (100 - VRATE_CLAMP_ADJ_PCT), 100);
1019 vrate = max(vrate, vrate_max);
1020 } else {
1021 int idx = min_t(int, abs(ioc->busy_level),
1022 ARRAY_SIZE(vrate_adj_pct) - 1);
1023 u32 adj_pct = vrate_adj_pct[idx];
1024
1025 if (ioc->busy_level > 0)
1026 adj_pct = 100 - adj_pct;
1027 else
1028 adj_pct = 100 + adj_pct;
1029
1030 vrate = clamp(DIV64_U64_ROUND_UP(vrate * adj_pct, 100),
1031 vrate_min, vrate_max);
1032 }
1033
1034 trace_iocost_ioc_vrate_adj(ioc, vrate, missed_ppm, rq_wait_pct,
1035 nr_lagging, nr_shortages);
1036
1037 ioc->vtime_base_rate = vrate;
1038 ioc_refresh_margins(ioc);
1039 }
1040
1041 /* take a snapshot of the current [v]time and vrate */
1042 static void ioc_now(struct ioc *ioc, struct ioc_now *now)
1043 {
1044 unsigned seq;
1045 u64 vrate;
1046
1047 now->now_ns = blk_time_get_ns();
1048 now->now = ktime_to_us(now->now_ns);
1049 vrate = atomic64_read(&ioc->vtime_rate);
1050
1051 /*
1052 * The current vtime is
1053 *
1054 * vtime at period start + (wallclock time since the start) * vrate
1055 *
1056 * As a consistent snapshot of `period_at_vtime` and `period_at` is
1057 * needed, they're seqcount protected.
1058 */
1059 do {
1060 seq = read_seqcount_begin(&ioc->period_seqcount);
1061 now->vnow = ioc->period_at_vtime +
1062 (now->now - ioc->period_at) * vrate;
1063 } while (read_seqcount_retry(&ioc->period_seqcount, seq));
1064 }
1065
1066 static void ioc_start_period(struct ioc *ioc, struct ioc_now *now)
1067 {
1068 WARN_ON_ONCE(ioc->running != IOC_RUNNING);
1069
1070 write_seqcount_begin(&ioc->period_seqcount);
1071 ioc->period_at = now->now;
1072 ioc->period_at_vtime = now->vnow;
1073 write_seqcount_end(&ioc->period_seqcount);
1074
1075 ioc->timer.expires = jiffies + usecs_to_jiffies(ioc->period_us);
1076 add_timer(&ioc->timer);
1077 }
1078
1079 /*
1080 * Update @iocg's `active` and `inuse` to @active and @inuse, update level
1081 * weight sums and propagate upwards accordingly. If @save, the current margin
1082 * is saved to be used as reference for later inuse in-period adjustments.
1083 */
1084 static void __propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse,
1085 bool save, struct ioc_now *now)
1086 {
1087 struct ioc *ioc = iocg->ioc;
1088 int lvl;
1089
1090 lockdep_assert_held(&ioc->lock);
1091
1092 /*
1093 * For an active leaf node, its inuse shouldn't be zero or exceed
1094 * @active. An active internal node's inuse is solely determined by the
1095 * inuse to active ratio of its children regardless of @inuse.
1096 */
1097 if (list_empty(&iocg->active_list) && iocg->child_active_sum) {
1098 inuse = DIV64_U64_ROUND_UP(active * iocg->child_inuse_sum,
1099 iocg->child_active_sum);
1100 } else {
1101 inuse = clamp_t(u32, inuse, 1, active);
1102 }
1103
1104 iocg->last_inuse = iocg->inuse;
1105 if (save)
1106 iocg->saved_margin = now->vnow - atomic64_read(&iocg->vtime);
1107
1108 if (active == iocg->active && inuse == iocg->inuse)
1109 return;
1110
1111 for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
1112 struct ioc_gq *parent = iocg->ancestors[lvl];
1113 struct ioc_gq *child = iocg->ancestors[lvl + 1];
1114 u32 parent_active = 0, parent_inuse = 0;
1115
1116 /* update the level sums */
1117 parent->child_active_sum += (s32)(active - child->active);
1118 parent->child_inuse_sum += (s32)(inuse - child->inuse);
1119 /* apply the updates */
1120 child->active = active;
1121 child->inuse = inuse;
1122
1123 /*
1124 * The delta between inuse and active sums indicates that
1125 * much of weight is being given away. Parent's inuse
1126 * and active should reflect the ratio.
1127 */
1128 if (parent->child_active_sum) {
1129 parent_active = parent->weight;
1130 parent_inuse = DIV64_U64_ROUND_UP(
1131 parent_active * parent->child_inuse_sum,
1132 parent->child_active_sum);
1133 }
1134
1135 /* do we need to keep walking up? */
1136 if (parent_active == parent->active &&
1137 parent_inuse == parent->inuse)
1138 break;
1139
1140 active = parent_active;
1141 inuse = parent_inuse;
1142 }
1143
1144 ioc->weights_updated = true;
1145 }
1146
1147 static void commit_weights(struct ioc *ioc)
1148 {
1149 lockdep_assert_held(&ioc->lock);
1150
1151 if (ioc->weights_updated) {
1152 /* paired with rmb in current_hweight(), see there */
1153 smp_wmb();
1154 atomic_inc(&ioc->hweight_gen);
1155 ioc->weights_updated = false;
1156 }
1157 }
1158
1159 static void propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse,
1160 bool save, struct ioc_now *now)
1161 {
1162 __propagate_weights(iocg, active, inuse, save, now);
1163 commit_weights(iocg->ioc);
1164 }
1165
1166 static void current_hweight(struct ioc_gq *iocg, u32 *hw_activep, u32 *hw_inusep)
1167 {
1168 struct ioc *ioc = iocg->ioc;
1169 int lvl;
1170 u32 hwa, hwi;
1171 int ioc_gen;
1172
1173 /* hot path - if uptodate, use cached */
1174 ioc_gen = atomic_read(&ioc->hweight_gen);
1175 if (ioc_gen == iocg->hweight_gen)
1176 goto out;
1177
1178 /*
1179 * Paired with wmb in commit_weights(). If we saw the updated
1180 * hweight_gen, all the weight updates from __propagate_weights() are
1181 * visible too.
1182 *
1183 * We can race with weight updates during calculation and get it
1184 * wrong. However, hweight_gen would have changed and a future
1185 * reader will recalculate and we're guaranteed to discard the
1186 * wrong result soon.
1187 */
1188 smp_rmb();
1189
1190 hwa = hwi = WEIGHT_ONE;
1191 for (lvl = 0; lvl <= iocg->level - 1; lvl++) {
1192 struct ioc_gq *parent = iocg->ancestors[lvl];
1193 struct ioc_gq *child = iocg->ancestors[lvl + 1];
1194 u64 active_sum = READ_ONCE(parent->child_active_sum);
1195 u64 inuse_sum = READ_ONCE(parent->child_inuse_sum);
1196 u32 active = READ_ONCE(child->active);
1197 u32 inuse = READ_ONCE(child->inuse);
1198
1199 /* we can race with deactivations and either may read as zero */
1200 if (!active_sum || !inuse_sum)
1201 continue;
1202
1203 active_sum = max_t(u64, active, active_sum);
1204 hwa = div64_u64((u64)hwa * active, active_sum);
1205
1206 inuse_sum = max_t(u64, inuse, inuse_sum);
1207 hwi = div64_u64((u64)hwi * inuse, inuse_sum);
1208 }
1209
1210 iocg->hweight_active = max_t(u32, hwa, 1);
1211 iocg->hweight_inuse = max_t(u32, hwi, 1);
1212 iocg->hweight_gen = ioc_gen;
1213 out:
1214 if (hw_activep)
1215 *hw_activep = iocg->hweight_active;
1216 if (hw_inusep)
1217 *hw_inusep = iocg->hweight_inuse;
1218 }
1219
1220 /*
1221 * Calculate the hweight_inuse @iocg would get with max @inuse assuming all the
1222 * other weights stay unchanged.
1223 */
1224 static u32 current_hweight_max(struct ioc_gq *iocg)
1225 {
1226 u32 hwm = WEIGHT_ONE;
1227 u32 inuse = iocg->active;
1228 u64 child_inuse_sum;
1229 int lvl;
1230
1231 lockdep_assert_held(&iocg->ioc->lock);
1232
1233 for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
1234 struct ioc_gq *parent = iocg->ancestors[lvl];
1235 struct ioc_gq *child = iocg->ancestors[lvl + 1];
1236
1237 child_inuse_sum = parent->child_inuse_sum + inuse - child->inuse;
1238 hwm = div64_u64((u64)hwm * inuse, child_inuse_sum);
1239 inuse = DIV64_U64_ROUND_UP(parent->active * child_inuse_sum,
1240 parent->child_active_sum);
1241 }
1242
1243 return max_t(u32, hwm, 1);
1244 }
1245
1246 static void weight_updated(struct ioc_gq *iocg, struct ioc_now *now)
1247 {
1248 struct ioc *ioc = iocg->ioc;
1249 struct blkcg_gq *blkg = iocg_to_blkg(iocg);
1250 struct ioc_cgrp *iocc = blkcg_to_iocc(blkg->blkcg);
1251 u32 weight;
1252
1253 lockdep_assert_held(&ioc->lock);
1254
1255 weight = iocg->cfg_weight ?: iocc->dfl_weight;
1256 if (weight != iocg->weight && iocg->active)
1257 propagate_weights(iocg, weight, iocg->inuse, true, now);
1258 iocg->weight = weight;
1259 }
1260
1261 static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now)
1262 {
1263 struct ioc *ioc = iocg->ioc;
1264 u64 __maybe_unused last_period, cur_period;
1265 u64 vtime, vtarget;
1266 int i;
1267
1268 /*
1269 * If seem to be already active, just update the stamp to tell the
1270 * timer that we're still active. We don't mind occassional races.
1271 */
1272 if (!list_empty(&iocg->active_list)) {
1273 ioc_now(ioc, now);
1274 cur_period = atomic64_read(&ioc->cur_period);
1275 if (atomic64_read(&iocg->active_period) != cur_period)
1276 atomic64_set(&iocg->active_period, cur_period);
1277 return true;
1278 }
1279
1280 /* racy check on internal node IOs, treat as root level IOs */
1281 if (iocg->child_active_sum)
1282 return false;
1283
1284 spin_lock_irq(&ioc->lock);
1285
1286 ioc_now(ioc, now);
1287
1288 /* update period */
1289 cur_period = atomic64_read(&ioc->cur_period);
1290 last_period = atomic64_read(&iocg->active_period);
1291 atomic64_set(&iocg->active_period, cur_period);
1292
1293 /* already activated or breaking leaf-only constraint? */
1294 if (!list_empty(&iocg->active_list))
1295 goto succeed_unlock;
1296 for (i = iocg->level - 1; i > 0; i--)
1297 if (!list_empty(&iocg->ancestors[i]->active_list))
1298 goto fail_unlock;
1299
1300 if (iocg->child_active_sum)
1301 goto fail_unlock;
1302
1303 /*
1304 * Always start with the target budget. On deactivation, we throw away
1305 * anything above it.
1306 */
1307 vtarget = now->vnow - ioc->margins.target;
1308 vtime = atomic64_read(&iocg->vtime);
1309
1310 atomic64_add(vtarget - vtime, &iocg->vtime);
1311 atomic64_add(vtarget - vtime, &iocg->done_vtime);
1312 vtime = vtarget;
1313
1314 /*
1315 * Activate, propagate weight and start period timer if not
1316 * running. Reset hweight_gen to avoid accidental match from
1317 * wrapping.
1318 */
1319 iocg->hweight_gen = atomic_read(&ioc->hweight_gen) - 1;
1320 list_add(&iocg->active_list, &ioc->active_iocgs);
1321
1322 propagate_weights(iocg, iocg->weight,
1323 iocg->last_inuse ?: iocg->weight, true, now);
1324
1325 TRACE_IOCG_PATH(iocg_activate, iocg, now,
1326 last_period, cur_period, vtime);
1327
1328 iocg->activated_at = now->now;
1329
1330 if (ioc->running == IOC_IDLE) {
1331 ioc->running = IOC_RUNNING;
1332 ioc->dfgv_period_at = now->now;
1333 ioc->dfgv_period_rem = 0;
1334 ioc_start_period(ioc, now);
1335 }
1336
1337 succeed_unlock:
1338 spin_unlock_irq(&ioc->lock);
1339 return true;
1340
1341 fail_unlock:
1342 spin_unlock_irq(&ioc->lock);
1343 return false;
1344 }
1345
1346 static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now)
1347 {
1348 struct ioc *ioc = iocg->ioc;
1349 struct blkcg_gq *blkg = iocg_to_blkg(iocg);
1350 u64 tdelta, delay, new_delay, shift;
1351 s64 vover, vover_pct;
1352 u32 hwa;
1353
1354 lockdep_assert_held(&iocg->waitq.lock);
1355
1356 /*
1357 * If the delay is set by another CPU, we may be in the past. No need to
1358 * change anything if so. This avoids decay calculation underflow.
1359 */
1360 if (time_before64(now->now, iocg->delay_at))
1361 return false;
1362
1363 /* calculate the current delay in effect - 1/2 every second */
1364 tdelta = now->now - iocg->delay_at;
1365 shift = div64_u64(tdelta, USEC_PER_SEC);
1366 if (iocg->delay && shift < BITS_PER_LONG)
1367 delay = iocg->delay >> shift;
1368 else
1369 delay = 0;
1370
1371 /* calculate the new delay from the debt amount */
1372 current_hweight(iocg, &hwa, NULL);
1373 vover = atomic64_read(&iocg->vtime) +
1374 abs_cost_to_cost(iocg->abs_vdebt, hwa) - now->vnow;
1375 vover_pct = div64_s64(100 * vover,
1376 ioc->period_us * ioc->vtime_base_rate);
1377
1378 if (vover_pct <= MIN_DELAY_THR_PCT)
1379 new_delay = 0;
1380 else if (vover_pct >= MAX_DELAY_THR_PCT)
1381 new_delay = MAX_DELAY;
1382 else
1383 new_delay = MIN_DELAY +
1384 div_u64((MAX_DELAY - MIN_DELAY) *
1385 (vover_pct - MIN_DELAY_THR_PCT),
1386 MAX_DELAY_THR_PCT - MIN_DELAY_THR_PCT);
1387
1388 /* pick the higher one and apply */
1389 if (new_delay > delay) {
1390 iocg->delay = new_delay;
1391 iocg->delay_at = now->now;
1392 delay = new_delay;
1393 }
1394
1395 if (delay >= MIN_DELAY) {
1396 if (!iocg->indelay_since)
1397 iocg->indelay_since = now->now;
1398 blkcg_set_delay(blkg, delay * NSEC_PER_USEC);
1399 return true;
1400 } else {
1401 if (iocg->indelay_since) {
1402 iocg->stat.indelay_us += now->now - iocg->indelay_since;
1403 iocg->indelay_since = 0;
1404 }
1405 iocg->delay = 0;
1406 blkcg_clear_delay(blkg);
1407 return false;
1408 }
1409 }
1410
1411 static void iocg_incur_debt(struct ioc_gq *iocg, u64 abs_cost,
1412 struct ioc_now *now)
1413 {
1414 struct iocg_pcpu_stat *gcs;
1415
1416 lockdep_assert_held(&iocg->ioc->lock);
1417 lockdep_assert_held(&iocg->waitq.lock);
1418 WARN_ON_ONCE(list_empty(&iocg->active_list));
1419
1420 /*
1421 * Once in debt, debt handling owns inuse. @iocg stays at the minimum
1422 * inuse donating all of it share to others until its debt is paid off.
1423 */
1424 if (!iocg->abs_vdebt && abs_cost) {
1425 iocg->indebt_since = now->now;
1426 propagate_weights(iocg, iocg->active, 0, false, now);
1427 }
1428
1429 iocg->abs_vdebt += abs_cost;
1430
1431 gcs = get_cpu_ptr(iocg->pcpu_stat);
1432 local64_add(abs_cost, &gcs->abs_vusage);
1433 put_cpu_ptr(gcs);
1434 }
1435
1436 static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay,
1437 struct ioc_now *now)
1438 {
1439 lockdep_assert_held(&iocg->ioc->lock);
1440 lockdep_assert_held(&iocg->waitq.lock);
1441
1442 /*
1443 * make sure that nobody messed with @iocg. Check iocg->pd.online
1444 * to avoid warn when removing blkcg or disk.
1445 */
1446 WARN_ON_ONCE(list_empty(&iocg->active_list) && iocg->pd.online);
1447 WARN_ON_ONCE(iocg->inuse > 1);
1448
1449 iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt);
1450
1451 /* if debt is paid in full, restore inuse */
1452 if (!iocg->abs_vdebt) {
1453 iocg->stat.indebt_us += now->now - iocg->indebt_since;
1454 iocg->indebt_since = 0;
1455
1456 propagate_weights(iocg, iocg->active, iocg->last_inuse,
1457 false, now);
1458 }
1459 }
1460
1461 static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode,
1462 int flags, void *key)
1463 {
1464 struct iocg_wait *wait = container_of(wq_entry, struct iocg_wait, wait);
1465 struct iocg_wake_ctx *ctx = key;
1466 u64 cost = abs_cost_to_cost(wait->abs_cost, ctx->hw_inuse);
1467
1468 ctx->vbudget -= cost;
1469
1470 if (ctx->vbudget < 0)
1471 return -1;
1472
1473 iocg_commit_bio(ctx->iocg, wait->bio, wait->abs_cost, cost);
1474 wait->committed = true;
1475
1476 /*
1477 * autoremove_wake_function() removes the wait entry only when it
1478 * actually changed the task state. We want the wait always removed.
1479 * Remove explicitly and use default_wake_function(). Note that the
1480 * order of operations is important as finish_wait() tests whether
1481 * @wq_entry is removed without grabbing the lock.
1482 */
1483 default_wake_function(wq_entry, mode, flags, key);
1484 list_del_init_careful(&wq_entry->entry);
1485 return 0;
1486 }
1487
1488 /*
1489 * Calculate the accumulated budget, pay debt if @pay_debt and wake up waiters
1490 * accordingly. When @pay_debt is %true, the caller must be holding ioc->lock in
1491 * addition to iocg->waitq.lock.
1492 */
1493 static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt,
1494 struct ioc_now *now)
1495 {
1496 struct ioc *ioc = iocg->ioc;
1497 struct iocg_wake_ctx ctx = { .iocg = iocg };
1498 u64 vshortage, expires, oexpires;
1499 s64 vbudget;
1500 u32 hwa;
1501
1502 lockdep_assert_held(&iocg->waitq.lock);
1503
1504 current_hweight(iocg, &hwa, NULL);
1505 vbudget = now->vnow - atomic64_read(&iocg->vtime);
1506
1507 /* pay off debt */
1508 if (pay_debt && iocg->abs_vdebt && vbudget > 0) {
1509 u64 abs_vbudget = cost_to_abs_cost(vbudget, hwa);
1510 u64 abs_vpay = min_t(u64, abs_vbudget, iocg->abs_vdebt);
1511 u64 vpay = abs_cost_to_cost(abs_vpay, hwa);
1512
1513 lockdep_assert_held(&ioc->lock);
1514
1515 atomic64_add(vpay, &iocg->vtime);
1516 atomic64_add(vpay, &iocg->done_vtime);
1517 iocg_pay_debt(iocg, abs_vpay, now);
1518 vbudget -= vpay;
1519 }
1520
1521 if (iocg->abs_vdebt || iocg->delay)
1522 iocg_kick_delay(iocg, now);
1523
1524 /*
1525 * Debt can still be outstanding if we haven't paid all yet or the
1526 * caller raced and called without @pay_debt. Shouldn't wake up waiters
1527 * under debt. Make sure @vbudget reflects the outstanding amount and is
1528 * not positive.
1529 */
1530 if (iocg->abs_vdebt) {
1531 s64 vdebt = abs_cost_to_cost(iocg->abs_vdebt, hwa);
1532 vbudget = min_t(s64, 0, vbudget - vdebt);
1533 }
1534
1535 /*
1536 * Wake up the ones which are due and see how much vtime we'll need for
1537 * the next one. As paying off debt restores hw_inuse, it must be read
1538 * after the above debt payment.
1539 */
1540 ctx.vbudget = vbudget;
1541 current_hweight(iocg, NULL, &ctx.hw_inuse);
1542
1543 __wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx);
1544
1545 if (!waitqueue_active(&iocg->waitq)) {
1546 if (iocg->wait_since) {
1547 iocg->stat.wait_us += now->now - iocg->wait_since;
1548 iocg->wait_since = 0;
1549 }
1550 return;
1551 }
1552
1553 if (!iocg->wait_since)
1554 iocg->wait_since = now->now;
1555
1556 if (WARN_ON_ONCE(ctx.vbudget >= 0))
1557 return;
1558
1559 /* determine next wakeup, add a timer margin to guarantee chunking */
1560 vshortage = -ctx.vbudget;
1561 expires = now->now_ns +
1562 DIV64_U64_ROUND_UP(vshortage, ioc->vtime_base_rate) *
1563 NSEC_PER_USEC;
1564 expires += ioc->timer_slack_ns;
1565
1566 /* if already active and close enough, don't bother */
1567 oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->waitq_timer));
1568 if (hrtimer_is_queued(&iocg->waitq_timer) &&
1569 abs(oexpires - expires) <= ioc->timer_slack_ns)
1570 return;
1571
1572 hrtimer_start_range_ns(&iocg->waitq_timer, ns_to_ktime(expires),
1573 ioc->timer_slack_ns, HRTIMER_MODE_ABS);
1574 }
1575
1576 static enum hrtimer_restart iocg_waitq_timer_fn(struct hrtimer *timer)
1577 {
1578 struct ioc_gq *iocg = container_of(timer, struct ioc_gq, waitq_timer);
1579 bool pay_debt = READ_ONCE(iocg->abs_vdebt);
1580 struct ioc_now now;
1581 unsigned long flags;
1582
1583 ioc_now(iocg->ioc, &now);
1584
1585 iocg_lock(iocg, pay_debt, &flags);
1586 iocg_kick_waitq(iocg, pay_debt, &now);
1587 iocg_unlock(iocg, pay_debt, &flags);
1588
1589 return HRTIMER_NORESTART;
1590 }
1591
1592 static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p)
1593 {
1594 u32 nr_met[2] = { };
1595 u32 nr_missed[2] = { };
1596 u64 rq_wait_ns = 0;
1597 int cpu, rw;
1598
1599 for_each_online_cpu(cpu) {
1600 struct ioc_pcpu_stat *stat = per_cpu_ptr(ioc->pcpu_stat, cpu);
1601 u64 this_rq_wait_ns;
1602
1603 for (rw = READ; rw <= WRITE; rw++) {
1604 u32 this_met = local_read(&stat->missed[rw].nr_met);
1605 u32 this_missed = local_read(&stat->missed[rw].nr_missed);
1606
1607 nr_met[rw] += this_met - stat->missed[rw].last_met;
1608 nr_missed[rw] += this_missed - stat->missed[rw].last_missed;
1609 stat->missed[rw].last_met = this_met;
1610 stat->missed[rw].last_missed = this_missed;
1611 }
1612
1613 this_rq_wait_ns = local64_read(&stat->rq_wait_ns);
1614 rq_wait_ns += this_rq_wait_ns - stat->last_rq_wait_ns;
1615 stat->last_rq_wait_ns = this_rq_wait_ns;
1616 }
1617
1618 for (rw = READ; rw <= WRITE; rw++) {
1619 if (nr_met[rw] + nr_missed[rw])
1620 missed_ppm_ar[rw] =
1621 DIV64_U64_ROUND_UP((u64)nr_missed[rw] * MILLION,
1622 nr_met[rw] + nr_missed[rw]);
1623 else
1624 missed_ppm_ar[rw] = 0;
1625 }
1626
1627 *rq_wait_pct_p = div64_u64(rq_wait_ns * 100,
1628 ioc->period_us * NSEC_PER_USEC);
1629 }
1630
1631 /* was iocg idle this period? */
1632 static bool iocg_is_idle(struct ioc_gq *iocg)
1633 {
1634 struct ioc *ioc = iocg->ioc;
1635
1636 /* did something get issued this period? */
1637 if (atomic64_read(&iocg->active_period) ==
1638 atomic64_read(&ioc->cur_period))
1639 return false;
1640
1641 /* is something in flight? */
1642 if (atomic64_read(&iocg->done_vtime) != atomic64_read(&iocg->vtime))
1643 return false;
1644
1645 return true;
1646 }
1647
1648 /*
1649 * Call this function on the target leaf @iocg's to build pre-order traversal
1650 * list of all the ancestors in @inner_walk. The inner nodes are linked through
1651 * ->walk_list and the caller is responsible for dissolving the list after use.
1652 */
1653 static void iocg_build_inner_walk(struct ioc_gq *iocg,
1654 struct list_head *inner_walk)
1655 {
1656 int lvl;
1657
1658 WARN_ON_ONCE(!list_empty(&iocg->walk_list));
1659
1660 /* find the first ancestor which hasn't been visited yet */
1661 for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
1662 if (!list_empty(&iocg->ancestors[lvl]->walk_list))
1663 break;
1664 }
1665
1666 /* walk down and visit the inner nodes to get pre-order traversal */
1667 while (++lvl <= iocg->level - 1) {
1668 struct ioc_gq *inner = iocg->ancestors[lvl];
1669
1670 /* record traversal order */
1671 list_add_tail(&inner->walk_list, inner_walk);
1672 }
1673 }
1674
1675 /* propagate the deltas to the parent */
1676 static void iocg_flush_stat_upward(struct ioc_gq *iocg)
1677 {
1678 if (iocg->level > 0) {
1679 struct iocg_stat *parent_stat =
1680 &iocg->ancestors[iocg->level - 1]->stat;
1681
1682 parent_stat->usage_us +=
1683 iocg->stat.usage_us - iocg->last_stat.usage_us;
1684 parent_stat->wait_us +=
1685 iocg->stat.wait_us - iocg->last_stat.wait_us;
1686 parent_stat->indebt_us +=
1687 iocg->stat.indebt_us - iocg->last_stat.indebt_us;
1688 parent_stat->indelay_us +=
1689 iocg->stat.indelay_us - iocg->last_stat.indelay_us;
1690 }
1691
1692 iocg->last_stat = iocg->stat;
1693 }
1694
1695 /* collect per-cpu counters and propagate the deltas to the parent */
1696 static void iocg_flush_stat_leaf(struct ioc_gq *iocg, struct ioc_now *now)
1697 {
1698 struct ioc *ioc = iocg->ioc;
1699 u64 abs_vusage = 0;
1700 u64 vusage_delta;
1701 int cpu;
1702
1703 lockdep_assert_held(&iocg->ioc->lock);
1704
1705 /* collect per-cpu counters */
1706 for_each_possible_cpu(cpu) {
1707 abs_vusage += local64_read(
1708 per_cpu_ptr(&iocg->pcpu_stat->abs_vusage, cpu));
1709 }
1710 vusage_delta = abs_vusage - iocg->last_stat_abs_vusage;
1711 iocg->last_stat_abs_vusage = abs_vusage;
1712
1713 iocg->usage_delta_us = div64_u64(vusage_delta, ioc->vtime_base_rate);
1714 iocg->stat.usage_us += iocg->usage_delta_us;
1715
1716 iocg_flush_stat_upward(iocg);
1717 }
1718
1719 /* get stat counters ready for reading on all active iocgs */
1720 static void iocg_flush_stat(struct list_head *target_iocgs, struct ioc_now *now)
1721 {
1722 LIST_HEAD(inner_walk);
1723 struct ioc_gq *iocg, *tiocg;
1724
1725 /* flush leaves and build inner node walk list */
1726 list_for_each_entry(iocg, target_iocgs, active_list) {
1727 iocg_flush_stat_leaf(iocg, now);
1728 iocg_build_inner_walk(iocg, &inner_walk);
1729 }
1730
1731 /* keep flushing upwards by walking the inner list backwards */
1732 list_for_each_entry_safe_reverse(iocg, tiocg, &inner_walk, walk_list) {
1733 iocg_flush_stat_upward(iocg);
1734 list_del_init(&iocg->walk_list);
1735 }
1736 }
1737
1738 /*
1739 * Determine what @iocg's hweight_inuse should be after donating unused
1740 * capacity. @hwm is the upper bound and used to signal no donation. This
1741 * function also throws away @iocg's excess budget.
1742 */
1743 static u32 hweight_after_donation(struct ioc_gq *iocg, u32 old_hwi, u32 hwm,
1744 u32 usage, struct ioc_now *now)
1745 {
1746 struct ioc *ioc = iocg->ioc;
1747 u64 vtime = atomic64_read(&iocg->vtime);
1748 s64 excess, delta, target, new_hwi;
1749
1750 /* debt handling owns inuse for debtors */
1751 if (iocg->abs_vdebt)
1752 return 1;
1753
1754 /* see whether minimum margin requirement is met */
1755 if (waitqueue_active(&iocg->waitq) ||
1756 time_after64(vtime, now->vnow - ioc->margins.min))
1757 return hwm;
1758
1759 /* throw away excess above target */
1760 excess = now->vnow - vtime - ioc->margins.target;
1761 if (excess > 0) {
1762 atomic64_add(excess, &iocg->vtime);
1763 atomic64_add(excess, &iocg->done_vtime);
1764 vtime += excess;
1765 ioc->vtime_err -= div64_u64(excess * old_hwi, WEIGHT_ONE);
1766 }
1767
1768 /*
1769 * Let's say the distance between iocg's and device's vtimes as a
1770 * fraction of period duration is delta. Assuming that the iocg will
1771 * consume the usage determined above, we want to determine new_hwi so
1772 * that delta equals MARGIN_TARGET at the end of the next period.
1773 *
1774 * We need to execute usage worth of IOs while spending the sum of the
1775 * new budget (1 - MARGIN_TARGET) and the leftover from the last period
1776 * (delta):
1777 *
1778 * usage = (1 - MARGIN_TARGET + delta) * new_hwi
1779 *
1780 * Therefore, the new_hwi is:
1781 *
1782 * new_hwi = usage / (1 - MARGIN_TARGET + delta)
1783 */
1784 delta = div64_s64(WEIGHT_ONE * (now->vnow - vtime),
1785 now->vnow - ioc->period_at_vtime);
1786 target = WEIGHT_ONE * MARGIN_TARGET_PCT / 100;
1787 new_hwi = div64_s64(WEIGHT_ONE * usage, WEIGHT_ONE - target + delta);
1788
1789 return clamp_t(s64, new_hwi, 1, hwm);
1790 }
1791
1792 /*
1793 * For work-conservation, an iocg which isn't using all of its share should
1794 * donate the leftover to other iocgs. There are two ways to achieve this - 1.
1795 * bumping up vrate accordingly 2. lowering the donating iocg's inuse weight.
1796 *
1797 * #1 is mathematically simpler but has the drawback of requiring synchronous
1798 * global hweight_inuse updates when idle iocg's get activated or inuse weights
1799 * change due to donation snapbacks as it has the possibility of grossly
1800 * overshooting what's allowed by the model and vrate.
1801 *
1802 * #2 is inherently safe with local operations. The donating iocg can easily
1803 * snap back to higher weights when needed without worrying about impacts on
1804 * other nodes as the impacts will be inherently correct. This also makes idle
1805 * iocg activations safe. The only effect activations have is decreasing
1806 * hweight_inuse of others, the right solution to which is for those iocgs to
1807 * snap back to higher weights.
1808 *
1809 * So, we go with #2. The challenge is calculating how each donating iocg's
1810 * inuse should be adjusted to achieve the target donation amounts. This is done
1811 * using Andy's method described in the following pdf.
1812 *
1813 * https://drive.google.com/file/d/1PsJwxPFtjUnwOY1QJ5AeICCcsL7BM3bo
1814 *
1815 * Given the weights and target after-donation hweight_inuse values, Andy's
1816 * method determines how the proportional distribution should look like at each
1817 * sibling level to maintain the relative relationship between all non-donating
1818 * pairs. To roughly summarize, it divides the tree into donating and
1819 * non-donating parts, calculates global donation rate which is used to
1820 * determine the target hweight_inuse for each node, and then derives per-level
1821 * proportions.
1822 *
1823 * The following pdf shows that global distribution calculated this way can be
1824 * achieved by scaling inuse weights of donating leaves and propagating the
1825 * adjustments upwards proportionally.
1826 *
1827 * https://drive.google.com/file/d/1vONz1-fzVO7oY5DXXsLjSxEtYYQbOvsE
1828 *
1829 * Combining the above two, we can determine how each leaf iocg's inuse should
1830 * be adjusted to achieve the target donation.
1831 *
1832 * https://drive.google.com/file/d/1WcrltBOSPN0qXVdBgnKm4mdp9FhuEFQN
1833 *
1834 * The inline comments use symbols from the last pdf.
1835 *
1836 * b is the sum of the absolute budgets in the subtree. 1 for the root node.
1837 * f is the sum of the absolute budgets of non-donating nodes in the subtree.
1838 * t is the sum of the absolute budgets of donating nodes in the subtree.
1839 * w is the weight of the node. w = w_f + w_t
1840 * w_f is the non-donating portion of w. w_f = w * f / b
1841 * w_b is the donating portion of w. w_t = w * t / b
1842 * s is the sum of all sibling weights. s = Sum(w) for siblings
1843 * s_f and s_t are the non-donating and donating portions of s.
1844 *
1845 * Subscript p denotes the parent's counterpart and ' the adjusted value - e.g.
1846 * w_pt is the donating portion of the parent's weight and w'_pt the same value
1847 * after adjustments. Subscript r denotes the root node's values.
1848 */
1849 static void transfer_surpluses(struct list_head *surpluses, struct ioc_now *now)
1850 {
1851 LIST_HEAD(over_hwa);
1852 LIST_HEAD(inner_walk);
1853 struct ioc_gq *iocg, *tiocg, *root_iocg;
1854 u32 after_sum, over_sum, over_target, gamma;
1855
1856 /*
1857 * It's pretty unlikely but possible for the total sum of
1858 * hweight_after_donation's to be higher than WEIGHT_ONE, which will
1859 * confuse the following calculations. If such condition is detected,
1860 * scale down everyone over its full share equally to keep the sum below
1861 * WEIGHT_ONE.
1862 */
1863 after_sum = 0;
1864 over_sum = 0;
1865 list_for_each_entry(iocg, surpluses, surplus_list) {
1866 u32 hwa;
1867
1868 current_hweight(iocg, &hwa, NULL);
1869 after_sum += iocg->hweight_after_donation;
1870
1871 if (iocg->hweight_after_donation > hwa) {
1872 over_sum += iocg->hweight_after_donation;
1873 list_add(&iocg->walk_list, &over_hwa);
1874 }
1875 }
1876
1877 if (after_sum >= WEIGHT_ONE) {
1878 /*
1879 * The delta should be deducted from the over_sum, calculate
1880 * target over_sum value.
1881 */
1882 u32 over_delta = after_sum - (WEIGHT_ONE - 1);
1883 WARN_ON_ONCE(over_sum <= over_delta);
1884 over_target = over_sum - over_delta;
1885 } else {
1886 over_target = 0;
1887 }
1888
1889 list_for_each_entry_safe(iocg, tiocg, &over_hwa, walk_list) {
1890 if (over_target)
1891 iocg->hweight_after_donation =
1892 div_u64((u64)iocg->hweight_after_donation *
1893 over_target, over_sum);
1894 list_del_init(&iocg->walk_list);
1895 }
1896
1897 /*
1898 * Build pre-order inner node walk list and prepare for donation
1899 * adjustment calculations.
1900 */
1901 list_for_each_entry(iocg, surpluses, surplus_list) {
1902 iocg_build_inner_walk(iocg, &inner_walk);
1903 }
1904
1905 root_iocg = list_first_entry(&inner_walk, struct ioc_gq, walk_list);
1906 WARN_ON_ONCE(root_iocg->level > 0);
1907
1908 list_for_each_entry(iocg, &inner_walk, walk_list) {
1909 iocg->child_adjusted_sum = 0;
1910 iocg->hweight_donating = 0;
1911 iocg->hweight_after_donation = 0;
1912 }
1913
1914 /*
1915 * Propagate the donating budget (b_t) and after donation budget (b'_t)
1916 * up the hierarchy.
1917 */
1918 list_for_each_entry(iocg, surpluses, surplus_list) {
1919 struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
1920
1921 parent->hweight_donating += iocg->hweight_donating;
1922 parent->hweight_after_donation += iocg->hweight_after_donation;
1923 }
1924
1925 list_for_each_entry_reverse(iocg, &inner_walk, walk_list) {
1926 if (iocg->level > 0) {
1927 struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
1928
1929 parent->hweight_donating += iocg->hweight_donating;
1930 parent->hweight_after_donation += iocg->hweight_after_donation;
1931 }
1932 }
1933
1934 /*
1935 * Calculate inner hwa's (b) and make sure the donation values are
1936 * within the accepted ranges as we're doing low res calculations with
1937 * roundups.
1938 */
1939 list_for_each_entry(iocg, &inner_walk, walk_list) {
1940 if (iocg->level) {
1941 struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
1942
1943 iocg->hweight_active = DIV64_U64_ROUND_UP(
1944 (u64)parent->hweight_active * iocg->active,
1945 parent->child_active_sum);
1946
1947 }
1948
1949 iocg->hweight_donating = min(iocg->hweight_donating,
1950 iocg->hweight_active);
1951 iocg->hweight_after_donation = min(iocg->hweight_after_donation,
1952 iocg->hweight_donating - 1);
1953 if (WARN_ON_ONCE(iocg->hweight_active <= 1 ||
1954 iocg->hweight_donating <= 1 ||
1955 iocg->hweight_after_donation == 0)) {
1956 pr_warn("iocg: invalid donation weights in ");
1957 pr_cont_cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup);
1958 pr_cont(": active=%u donating=%u after=%u\n",
1959 iocg->hweight_active, iocg->hweight_donating,
1960 iocg->hweight_after_donation);
1961 }
1962 }
1963
1964 /*
1965 * Calculate the global donation rate (gamma) - the rate to adjust
1966 * non-donating budgets by.
1967 *
1968 * No need to use 64bit multiplication here as the first operand is
1969 * guaranteed to be smaller than WEIGHT_ONE (1<<16).
1970 *
1971 * We know that there are beneficiary nodes and the sum of the donating
1972 * hweights can't be whole; however, due to the round-ups during hweight
1973 * calculations, root_iocg->hweight_donating might still end up equal to
1974 * or greater than whole. Limit the range when calculating the divider.
1975 *
1976 * gamma = (1 - t_r') / (1 - t_r)
1977 */
1978 gamma = DIV_ROUND_UP(
1979 (WEIGHT_ONE - root_iocg->hweight_after_donation) * WEIGHT_ONE,
1980 WEIGHT_ONE - min_t(u32, root_iocg->hweight_donating, WEIGHT_ONE - 1));
1981
1982 /*
1983 * Calculate adjusted hwi, child_adjusted_sum and inuse for the inner
1984 * nodes.
1985 */
1986 list_for_each_entry(iocg, &inner_walk, walk_list) {
1987 struct ioc_gq *parent;
1988 u32 inuse, wpt, wptp;
1989 u64 st, sf;
1990
1991 if (iocg->level == 0) {
1992 /* adjusted weight sum for 1st level: s' = s * b_pf / b'_pf */
1993 iocg->child_adjusted_sum = DIV64_U64_ROUND_UP(
1994 iocg->child_active_sum * (WEIGHT_ONE - iocg->hweight_donating),
1995 WEIGHT_ONE - iocg->hweight_after_donation);
1996 continue;
1997 }
1998
1999 parent = iocg->ancestors[iocg->level - 1];
2000
2001 /* b' = gamma * b_f + b_t' */
2002 iocg->hweight_inuse = DIV64_U64_ROUND_UP(
2003 (u64)gamma * (iocg->hweight_active - iocg->hweight_donating),
2004 WEIGHT_ONE) + iocg->hweight_after_donation;
2005
2006 /* w' = s' * b' / b'_p */
2007 inuse = DIV64_U64_ROUND_UP(
2008 (u64)parent->child_adjusted_sum * iocg->hweight_inuse,
2009 parent->hweight_inuse);
2010
2011 /* adjusted weight sum for children: s' = s_f + s_t * w'_pt / w_pt */
2012 st = DIV64_U64_ROUND_UP(
2013 iocg->child_active_sum * iocg->hweight_donating,
2014 iocg->hweight_active);
2015 sf = iocg->child_active_sum - st;
2016 wpt = DIV64_U64_ROUND_UP(
2017 (u64)iocg->active * iocg->hweight_donating,
2018 iocg->hweight_active);
2019 wptp = DIV64_U64_ROUND_UP(
2020 (u64)inuse * iocg->hweight_after_donation,
2021 iocg->hweight_inuse);
2022
2023 iocg->child_adjusted_sum = sf + DIV64_U64_ROUND_UP(st * wptp, wpt);
2024 }
2025
2026 /*
2027 * All inner nodes now have ->hweight_inuse and ->child_adjusted_sum and
2028 * we can finally determine leaf adjustments.
2029 */
2030 list_for_each_entry(iocg, surpluses, surplus_list) {
2031 struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
2032 u32 inuse;
2033
2034 /*
2035 * In-debt iocgs participated in the donation calculation with
2036 * the minimum target hweight_inuse. Configuring inuse
2037 * accordingly would work fine but debt handling expects
2038 * @iocg->inuse stay at the minimum and we don't wanna
2039 * interfere.
2040 */
2041 if (iocg->abs_vdebt) {
2042 WARN_ON_ONCE(iocg->inuse > 1);
2043 continue;
2044 }
2045
2046 /* w' = s' * b' / b'_p, note that b' == b'_t for donating leaves */
2047 inuse = DIV64_U64_ROUND_UP(
2048 parent->child_adjusted_sum * iocg->hweight_after_donation,
2049 parent->hweight_inuse);
2050
2051 TRACE_IOCG_PATH(inuse_transfer, iocg, now,
2052 iocg->inuse, inuse,
2053 iocg->hweight_inuse,
2054 iocg->hweight_after_donation);
2055
2056 __propagate_weights(iocg, iocg->active, inuse, true, now);
2057 }
2058
2059 /* walk list should be dissolved after use */
2060 list_for_each_entry_safe(iocg, tiocg, &inner_walk, walk_list)
2061 list_del_init(&iocg->walk_list);
2062 }
2063
2064 /*
2065 * A low weight iocg can amass a large amount of debt, for example, when
2066 * anonymous memory gets reclaimed aggressively. If the system has a lot of
2067 * memory paired with a slow IO device, the debt can span multiple seconds or
2068 * more. If there are no other subsequent IO issuers, the in-debt iocg may end
2069 * up blocked paying its debt while the IO device is idle.
2070 *
2071 * The following protects against such cases. If the device has been
2072 * sufficiently idle for a while, the debts are halved and delays are
2073 * recalculated.
2074 */
2075 static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors,
2076 struct ioc_now *now)
2077 {
2078 struct ioc_gq *iocg;
2079 u64 dur, usage_pct, nr_cycles, nr_cycles_shift;
2080
2081 /* if no debtor, reset the cycle */
2082 if (!nr_debtors) {
2083 ioc->dfgv_period_at = now->now;
2084 ioc->dfgv_period_rem = 0;
2085 ioc->dfgv_usage_us_sum = 0;
2086 return;
2087 }
2088
2089 /*
2090 * Debtors can pass through a lot of writes choking the device and we
2091 * don't want to be forgiving debts while the device is struggling from
2092 * write bursts. If we're missing latency targets, consider the device
2093 * fully utilized.
2094 */
2095 if (ioc->busy_level > 0)
2096 usage_us_sum = max_t(u64, usage_us_sum, ioc->period_us);
2097
2098 ioc->dfgv_usage_us_sum += usage_us_sum;
2099 if (time_before64(now->now, ioc->dfgv_period_at + DFGV_PERIOD))
2100 return;
2101
2102 /*
2103 * At least DFGV_PERIOD has passed since the last period. Calculate the
2104 * average usage and reset the period counters.
2105 */
2106 dur = now->now - ioc->dfgv_period_at;
2107 usage_pct = div64_u64(100 * ioc->dfgv_usage_us_sum, dur);
2108
2109 ioc->dfgv_period_at = now->now;
2110 ioc->dfgv_usage_us_sum = 0;
2111
2112 /* if was too busy, reset everything */
2113 if (usage_pct > DFGV_USAGE_PCT) {
2114 ioc->dfgv_period_rem = 0;
2115 return;
2116 }
2117
2118 /*
2119 * Usage is lower than threshold. Let's forgive some debts. Debt
2120 * forgiveness runs off of the usual ioc timer but its period usually
2121 * doesn't match ioc's. Compensate the difference by performing the
2122 * reduction as many times as would fit in the duration since the last
2123 * run and carrying over the left-over duration in @ioc->dfgv_period_rem
2124 * - if ioc period is 75% of DFGV_PERIOD, one out of three consecutive
2125 * reductions is doubled.
2126 */
2127 nr_cycles = dur + ioc->dfgv_period_rem;
2128 ioc->dfgv_period_rem = do_div(nr_cycles, DFGV_PERIOD);
2129
2130 list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
2131 u64 __maybe_unused old_debt, __maybe_unused old_delay;
2132
2133 if (!iocg->abs_vdebt && !iocg->delay)
2134 continue;
2135
2136 spin_lock(&iocg->waitq.lock);
2137
2138 old_debt = iocg->abs_vdebt;
2139 old_delay = iocg->delay;
2140
2141 nr_cycles_shift = min_t(u64, nr_cycles, BITS_PER_LONG - 1);
2142 if (iocg->abs_vdebt)
2143 iocg->abs_vdebt = iocg->abs_vdebt >> nr_cycles_shift ?: 1;
2144
2145 if (iocg->delay)
2146 iocg->delay = iocg->delay >> nr_cycles_shift ?: 1;
2147
2148 iocg_kick_waitq(iocg, true, now);
2149
2150 TRACE_IOCG_PATH(iocg_forgive_debt, iocg, now, usage_pct,
2151 old_debt, iocg->abs_vdebt,
2152 old_delay, iocg->delay);
2153
2154 spin_unlock(&iocg->waitq.lock);
2155 }
2156 }
2157
2158 /*
2159 * Check the active iocgs' state to avoid oversleeping and deactive
2160 * idle iocgs.
2161 *
2162 * Since waiters determine the sleep durations based on the vrate
2163 * they saw at the time of sleep, if vrate has increased, some
2164 * waiters could be sleeping for too long. Wake up tardy waiters
2165 * which should have woken up in the last period and expire idle
2166 * iocgs.
2167 */
2168 static int ioc_check_iocgs(struct ioc *ioc, struct ioc_now *now)
2169 {
2170 int nr_debtors = 0;
2171 struct ioc_gq *iocg, *tiocg;
2172
2173 list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) {
2174 if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt &&
2175 !iocg->delay && !iocg_is_idle(iocg))
2176 continue;
2177
2178 spin_lock(&iocg->waitq.lock);
2179
2180 /* flush wait and indebt stat deltas */
2181 if (iocg->wait_since) {
2182 iocg->stat.wait_us += now->now - iocg->wait_since;
2183 iocg->wait_since = now->now;
2184 }
2185 if (iocg->indebt_since) {
2186 iocg->stat.indebt_us +=
2187 now->now - iocg->indebt_since;
2188 iocg->indebt_since = now->now;
2189 }
2190 if (iocg->indelay_since) {
2191 iocg->stat.indelay_us +=
2192 now->now - iocg->indelay_since;
2193 iocg->indelay_since = now->now;
2194 }
2195
2196 if (waitqueue_active(&iocg->waitq) || iocg->abs_vdebt ||
2197 iocg->delay) {
2198 /* might be oversleeping vtime / hweight changes, kick */
2199 iocg_kick_waitq(iocg, true, now);
2200 if (iocg->abs_vdebt || iocg->delay)
2201 nr_debtors++;
2202 } else if (iocg_is_idle(iocg)) {
2203 /* no waiter and idle, deactivate */
2204 u64 vtime = atomic64_read(&iocg->vtime);
2205 s64 excess;
2206
2207 /*
2208 * @iocg has been inactive for a full duration and will
2209 * have a high budget. Account anything above target as
2210 * error and throw away. On reactivation, it'll start
2211 * with the target budget.
2212 */
2213 excess = now->vnow - vtime - ioc->margins.target;
2214 if (excess > 0) {
2215 u32 old_hwi;
2216
2217 current_hweight(iocg, NULL, &old_hwi);
2218 ioc->vtime_err -= div64_u64(excess * old_hwi,
2219 WEIGHT_ONE);
2220 }
2221
2222 TRACE_IOCG_PATH(iocg_idle, iocg, now,
2223 atomic64_read(&iocg->active_period),
2224 atomic64_read(&ioc->cur_period), vtime);
2225 __propagate_weights(iocg, 0, 0, false, now);
2226 list_del_init(&iocg->active_list);
2227 }
2228
2229 spin_unlock(&iocg->waitq.lock);
2230 }
2231
2232 commit_weights(ioc);
2233 return nr_debtors;
2234 }
2235
2236 static void ioc_timer_fn(struct timer_list *timer)
2237 {
2238 struct ioc *ioc = container_of(timer, struct ioc, timer);
2239 struct ioc_gq *iocg, *tiocg;
2240 struct ioc_now now;
2241 LIST_HEAD(surpluses);
2242 int nr_debtors, nr_shortages = 0, nr_lagging = 0;
2243 u64 usage_us_sum = 0;
2244 u32 ppm_rthr;
2245 u32 ppm_wthr;
2246 u32 missed_ppm[2], rq_wait_pct;
2247 u64 period_vtime;
2248 int prev_busy_level;
2249
2250 /* how were the latencies during the period? */
2251 ioc_lat_stat(ioc, missed_ppm, &rq_wait_pct);
2252
2253 /* take care of active iocgs */
2254 spin_lock_irq(&ioc->lock);
2255
2256 ppm_rthr = MILLION - ioc->params.qos[QOS_RPPM];
2257 ppm_wthr = MILLION - ioc->params.qos[QOS_WPPM];
2258 ioc_now(ioc, &now);
2259
2260 period_vtime = now.vnow - ioc->period_at_vtime;
2261 if (WARN_ON_ONCE(!period_vtime)) {
2262 spin_unlock_irq(&ioc->lock);
2263 return;
2264 }
2265
2266 nr_debtors = ioc_check_iocgs(ioc, &now);
2267
2268 /*
2269 * Wait and indebt stat are flushed above and the donation calculation
2270 * below needs updated usage stat. Let's bring stat up-to-date.
2271 */
2272 iocg_flush_stat(&ioc->active_iocgs, &now);
2273
2274 /* calc usage and see whether some weights need to be moved around */
2275 list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
2276 u64 vdone, vtime, usage_us;
2277 u32 hw_active, hw_inuse;
2278
2279 /*
2280 * Collect unused and wind vtime closer to vnow to prevent
2281 * iocgs from accumulating a large amount of budget.
2282 */
2283 vdone = atomic64_read(&iocg->done_vtime);
2284 vtime = atomic64_read(&iocg->vtime);
2285 current_hweight(iocg, &hw_active, &hw_inuse);
2286
2287 /*
2288 * Latency QoS detection doesn't account for IOs which are
2289 * in-flight for longer than a period. Detect them by
2290 * comparing vdone against period start. If lagging behind
2291 * IOs from past periods, don't increase vrate.
2292 */
2293 if ((ppm_rthr != MILLION || ppm_wthr != MILLION) &&
2294 !atomic_read(&iocg_to_blkg(iocg)->use_delay) &&
2295 time_after64(vtime, vdone) &&
2296 time_after64(vtime, now.vnow -
2297 MAX_LAGGING_PERIODS * period_vtime) &&
2298 time_before64(vdone, now.vnow - period_vtime))
2299 nr_lagging++;
2300
2301 /*
2302 * Determine absolute usage factoring in in-flight IOs to avoid
2303 * high-latency completions appearing as idle.
2304 */
2305 usage_us = iocg->usage_delta_us;
2306 usage_us_sum += usage_us;
2307
2308 /* see whether there's surplus vtime */
2309 WARN_ON_ONCE(!list_empty(&iocg->surplus_list));
2310 if (hw_inuse < hw_active ||
2311 (!waitqueue_active(&iocg->waitq) &&
2312 time_before64(vtime, now.vnow - ioc->margins.low))) {
2313 u32 hwa, old_hwi, hwm, new_hwi, usage;
2314 u64 usage_dur;
2315
2316 if (vdone != vtime) {
2317 u64 inflight_us = DIV64_U64_ROUND_UP(
2318 cost_to_abs_cost(vtime - vdone, hw_inuse),
2319 ioc->vtime_base_rate);
2320
2321 usage_us = max(usage_us, inflight_us);
2322 }
2323
2324 /* convert to hweight based usage ratio */
2325 if (time_after64(iocg->activated_at, ioc->period_at))
2326 usage_dur = max_t(u64, now.now - iocg->activated_at, 1);
2327 else
2328 usage_dur = max_t(u64, now.now - ioc->period_at, 1);
2329
2330 usage = clamp_t(u32,
2331 DIV64_U64_ROUND_UP(usage_us * WEIGHT_ONE,
2332 usage_dur),
2333 1, WEIGHT_ONE);
2334
2335 /*
2336 * Already donating or accumulated enough to start.
2337 * Determine the donation amount.
2338 */
2339 current_hweight(iocg, &hwa, &old_hwi);
2340 hwm = current_hweight_max(iocg);
2341 new_hwi = hweight_after_donation(iocg, old_hwi, hwm,
2342 usage, &now);
2343 /*
2344 * Donation calculation assumes hweight_after_donation
2345 * to be positive, a condition that a donor w/ hwa < 2
2346 * can't meet. Don't bother with donation if hwa is
2347 * below 2. It's not gonna make a meaningful difference
2348 * anyway.
2349 */
2350 if (new_hwi < hwm && hwa >= 2) {
2351 iocg->hweight_donating = hwa;
2352 iocg->hweight_after_donation = new_hwi;
2353 list_add(&iocg->surplus_list, &surpluses);
2354 } else if (!iocg->abs_vdebt) {
2355 /*
2356 * @iocg doesn't have enough to donate. Reset
2357 * its inuse to active.
2358 *
2359 * Don't reset debtors as their inuse's are
2360 * owned by debt handling. This shouldn't affect
2361 * donation calculuation in any meaningful way
2362 * as @iocg doesn't have a meaningful amount of
2363 * share anyway.
2364 */
2365 TRACE_IOCG_PATH(inuse_shortage, iocg, &now,
2366 iocg->inuse, iocg->active,
2367 iocg->hweight_inuse, new_hwi);
2368
2369 __propagate_weights(iocg, iocg->active,
2370 iocg->active, true, &now);
2371 nr_shortages++;
2372 }
2373 } else {
2374 /* genuinely short on vtime */
2375 nr_shortages++;
2376 }
2377 }
2378
2379 if (!list_empty(&surpluses) && nr_shortages)
2380 transfer_surpluses(&surpluses, &now);
2381
2382 commit_weights(ioc);
2383
2384 /* surplus list should be dissolved after use */
2385 list_for_each_entry_safe(iocg, tiocg, &surpluses, surplus_list)
2386 list_del_init(&iocg->surplus_list);
2387
2388 /*
2389 * If q is getting clogged or we're missing too much, we're issuing
2390 * too much IO and should lower vtime rate. If we're not missing
2391 * and experiencing shortages but not surpluses, we're too stingy
2392 * and should increase vtime rate.
2393 */
2394 prev_busy_level = ioc->busy_level;
2395 if (rq_wait_pct > RQ_WAIT_BUSY_PCT ||
2396 missed_ppm[READ] > ppm_rthr ||
2397 missed_ppm[WRITE] > ppm_wthr) {
2398 /* clearly missing QoS targets, slow down vrate */
2399 ioc->busy_level = max(ioc->busy_level, 0);
2400 ioc->busy_level++;
2401 } else if (rq_wait_pct <= RQ_WAIT_BUSY_PCT * UNBUSY_THR_PCT / 100 &&
2402 missed_ppm[READ] <= ppm_rthr * UNBUSY_THR_PCT / 100 &&
2403 missed_ppm[WRITE] <= ppm_wthr * UNBUSY_THR_PCT / 100) {
2404 /* QoS targets are being met with >25% margin */
2405 if (nr_shortages) {
2406 /*
2407 * We're throttling while the device has spare
2408 * capacity. If vrate was being slowed down, stop.
2409 */
2410 ioc->busy_level = min(ioc->busy_level, 0);
2411
2412 /*
2413 * If there are IOs spanning multiple periods, wait
2414 * them out before pushing the device harder.
2415 */
2416 if (!nr_lagging)
2417 ioc->busy_level--;
2418 } else {
2419 /*
2420 * Nobody is being throttled and the users aren't
2421 * issuing enough IOs to saturate the device. We
2422 * simply don't know how close the device is to
2423 * saturation. Coast.
2424 */
2425 ioc->busy_level = 0;
2426 }
2427 } else {
2428 /* inside the hysterisis margin, we're good */
2429 ioc->busy_level = 0;
2430 }
2431
2432 ioc->busy_level = clamp(ioc->busy_level, -1000, 1000);
2433
2434 ioc_adjust_base_vrate(ioc, rq_wait_pct, nr_lagging, nr_shortages,
2435 prev_busy_level, missed_ppm);
2436
2437 ioc_refresh_params(ioc, false);
2438
2439 ioc_forgive_debts(ioc, usage_us_sum, nr_debtors, &now);
2440
2441 /*
2442 * This period is done. Move onto the next one. If nothing's
2443 * going on with the device, stop the timer.
2444 */
2445 atomic64_inc(&ioc->cur_period);
2446
2447 if (ioc->running != IOC_STOP) {
2448 if (!list_empty(&ioc->active_iocgs)) {
2449 ioc_start_period(ioc, &now);
2450 } else {
2451 ioc->busy_level = 0;
2452 ioc->vtime_err = 0;
2453 ioc->running = IOC_IDLE;
2454 }
2455
2456 ioc_refresh_vrate(ioc, &now);
2457 }
2458
2459 spin_unlock_irq(&ioc->lock);
2460 }
2461
2462 static u64 adjust_inuse_and_calc_cost(struct ioc_gq *iocg, u64 vtime,
2463 u64 abs_cost, struct ioc_now *now)
2464 {
2465 struct ioc *ioc = iocg->ioc;
2466 struct ioc_margins *margins = &ioc->margins;
2467 u32 __maybe_unused old_inuse = iocg->inuse, __maybe_unused old_hwi;
2468 u32 hwi, adj_step;
2469 s64 margin;
2470 u64 cost, new_inuse;
2471 unsigned long flags;
2472
2473 current_hweight(iocg, NULL, &hwi);
2474 old_hwi = hwi;
2475 cost = abs_cost_to_cost(abs_cost, hwi);
2476 margin = now->vnow - vtime - cost;
2477
2478 /* debt handling owns inuse for debtors */
2479 if (iocg->abs_vdebt)
2480 return cost;
2481
2482 /*
2483 * We only increase inuse during period and do so if the margin has
2484 * deteriorated since the previous adjustment.
2485 */
2486 if (margin >= iocg->saved_margin || margin >= margins->low ||
2487 iocg->inuse == iocg->active)
2488 return cost;
2489
2490 spin_lock_irqsave(&ioc->lock, flags);
2491
2492 /* we own inuse only when @iocg is in the normal active state */
2493 if (iocg->abs_vdebt || list_empty(&iocg->active_list)) {
2494 spin_unlock_irqrestore(&ioc->lock, flags);
2495 return cost;
2496 }
2497
2498 /*
2499 * Bump up inuse till @abs_cost fits in the existing budget.
2500 * adj_step must be determined after acquiring ioc->lock - we might
2501 * have raced and lost to another thread for activation and could
2502 * be reading 0 iocg->active before ioc->lock which will lead to
2503 * infinite loop.
2504 */
2505 new_inuse = iocg->inuse;
2506 adj_step = DIV_ROUND_UP(iocg->active * INUSE_ADJ_STEP_PCT, 100);
2507 do {
2508 new_inuse = new_inuse + adj_step;
2509 propagate_weights(iocg, iocg->active, new_inuse, true, now);
2510 current_hweight(iocg, NULL, &hwi);
2511 cost = abs_cost_to_cost(abs_cost, hwi);
2512 } while (time_after64(vtime + cost, now->vnow) &&
2513 iocg->inuse != iocg->active);
2514
2515 spin_unlock_irqrestore(&ioc->lock, flags);
2516
2517 TRACE_IOCG_PATH(inuse_adjust, iocg, now,
2518 old_inuse, iocg->inuse, old_hwi, hwi);
2519
2520 return cost;
2521 }
2522
2523 static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg,
2524 bool is_merge, u64 *costp)
2525 {
2526 struct ioc *ioc = iocg->ioc;
2527 u64 coef_seqio, coef_randio, coef_page;
2528 u64 pages = max_t(u64, bio_sectors(bio) >> IOC_SECT_TO_PAGE_SHIFT, 1);
2529 u64 seek_pages = 0;
2530 u64 cost = 0;
2531
2532 /* Can't calculate cost for empty bio */
2533 if (!bio->bi_iter.bi_size)
2534 goto out;
2535
2536 switch (bio_op(bio)) {
2537 case REQ_OP_READ:
2538 coef_seqio = ioc->params.lcoefs[LCOEF_RSEQIO];
2539 coef_randio = ioc->params.lcoefs[LCOEF_RRANDIO];
2540 coef_page = ioc->params.lcoefs[LCOEF_RPAGE];
2541 break;
2542 case REQ_OP_WRITE:
2543 coef_seqio = ioc->params.lcoefs[LCOEF_WSEQIO];
2544 coef_randio = ioc->params.lcoefs[LCOEF_WRANDIO];
2545 coef_page = ioc->params.lcoefs[LCOEF_WPAGE];
2546 break;
2547 default:
2548 goto out;
2549 }
2550
2551 if (iocg->cursor) {
2552 seek_pages = abs(bio->bi_iter.bi_sector - iocg->cursor);
2553 seek_pages >>= IOC_SECT_TO_PAGE_SHIFT;
2554 }
2555
2556 if (!is_merge) {
2557 if (seek_pages > LCOEF_RANDIO_PAGES) {
2558 cost += coef_randio;
2559 } else {
2560 cost += coef_seqio;
2561 }
2562 }
2563 cost += pages * coef_page;
2564 out:
2565 *costp = cost;
2566 }
2567
2568 static u64 calc_vtime_cost(struct bio *bio, struct ioc_gq *iocg, bool is_merge)
2569 {
2570 u64 cost;
2571
2572 calc_vtime_cost_builtin(bio, iocg, is_merge, &cost);
2573 return cost;
2574 }
2575
2576 static void calc_size_vtime_cost_builtin(struct request *rq, struct ioc *ioc,
2577 u64 *costp)
2578 {
2579 unsigned int pages = blk_rq_stats_sectors(rq) >> IOC_SECT_TO_PAGE_SHIFT;
2580
2581 switch (req_op(rq)) {
2582 case REQ_OP_READ:
2583 *costp = pages * ioc->params.lcoefs[LCOEF_RPAGE];
2584 break;
2585 case REQ_OP_WRITE:
2586 *costp = pages * ioc->params.lcoefs[LCOEF_WPAGE];
2587 break;
2588 default:
2589 *costp = 0;
2590 }
2591 }
2592
2593 static u64 calc_size_vtime_cost(struct request *rq, struct ioc *ioc)
2594 {
2595 u64 cost;
2596
2597 calc_size_vtime_cost_builtin(rq, ioc, &cost);
2598 return cost;
2599 }
2600
2601 static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
2602 {
2603 struct blkcg_gq *blkg = bio->bi_blkg;
2604 struct ioc *ioc = rqos_to_ioc(rqos);
2605 struct ioc_gq *iocg = blkg_to_iocg(blkg);
2606 struct ioc_now now;
2607 struct iocg_wait wait;
2608 u64 abs_cost, cost, vtime;
2609 bool use_debt, ioc_locked;
2610 unsigned long flags;
2611
2612 /* bypass IOs if disabled, still initializing, or for root cgroup */
2613 if (!ioc->enabled || !iocg || !iocg->level)
2614 return;
2615
2616 /* calculate the absolute vtime cost */
2617 abs_cost = calc_vtime_cost(bio, iocg, false);
2618 if (!abs_cost)
2619 return;
2620
2621 if (!iocg_activate(iocg, &now))
2622 return;
2623
2624 iocg->cursor = bio_end_sector(bio);
2625 vtime = atomic64_read(&iocg->vtime);
2626 cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now);
2627
2628 /*
2629 * If no one's waiting and within budget, issue right away. The
2630 * tests are racy but the races aren't systemic - we only miss once
2631 * in a while which is fine.
2632 */
2633 if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt &&
2634 time_before_eq64(vtime + cost, now.vnow)) {
2635 iocg_commit_bio(iocg, bio, abs_cost, cost);
2636 return;
2637 }
2638
2639 /*
2640 * We're over budget. This can be handled in two ways. IOs which may
2641 * cause priority inversions are punted to @ioc->aux_iocg and charged as
2642 * debt. Otherwise, the issuer is blocked on @iocg->waitq. Debt handling
2643 * requires @ioc->lock, waitq handling @iocg->waitq.lock. Determine
2644 * whether debt handling is needed and acquire locks accordingly.
2645 */
2646 use_debt = bio_issue_as_root_blkg(bio) || fatal_signal_pending(current);
2647 ioc_locked = use_debt || READ_ONCE(iocg->abs_vdebt);
2648 retry_lock:
2649 iocg_lock(iocg, ioc_locked, &flags);
2650
2651 /*
2652 * @iocg must stay activated for debt and waitq handling. Deactivation
2653 * is synchronized against both ioc->lock and waitq.lock and we won't
2654 * get deactivated as long as we're waiting or has debt, so we're good
2655 * if we're activated here. In the unlikely cases that we aren't, just
2656 * issue the IO.
2657 */
2658 if (unlikely(list_empty(&iocg->active_list))) {
2659 iocg_unlock(iocg, ioc_locked, &flags);
2660 iocg_commit_bio(iocg, bio, abs_cost, cost);
2661 return;
2662 }
2663
2664 /*
2665 * We're over budget. If @bio has to be issued regardless, remember
2666 * the abs_cost instead of advancing vtime. iocg_kick_waitq() will pay
2667 * off the debt before waking more IOs.
2668 *
2669 * This way, the debt is continuously paid off each period with the
2670 * actual budget available to the cgroup. If we just wound vtime, we
2671 * would incorrectly use the current hw_inuse for the entire amount
2672 * which, for example, can lead to the cgroup staying blocked for a
2673 * long time even with substantially raised hw_inuse.
2674 *
2675 * An iocg with vdebt should stay online so that the timer can keep
2676 * deducting its vdebt and [de]activate use_delay mechanism
2677 * accordingly. We don't want to race against the timer trying to
2678 * clear them and leave @iocg inactive w/ dangling use_delay heavily
2679 * penalizing the cgroup and its descendants.
2680 */
2681 if (use_debt) {
2682 iocg_incur_debt(iocg, abs_cost, &now);
2683 if (iocg_kick_delay(iocg, &now))
2684 blkcg_schedule_throttle(rqos->disk,
2685 (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
2686 iocg_unlock(iocg, ioc_locked, &flags);
2687 return;
2688 }
2689
2690 /* guarantee that iocgs w/ waiters have maximum inuse */
2691 if (!iocg->abs_vdebt && iocg->inuse != iocg->active) {
2692 if (!ioc_locked) {
2693 iocg_unlock(iocg, false, &flags);
2694 ioc_locked = true;
2695 goto retry_lock;
2696 }
2697 propagate_weights(iocg, iocg->active, iocg->active, true,
2698 &now);
2699 }
2700
2701 /*
2702 * Append self to the waitq and schedule the wakeup timer if we're
2703 * the first waiter. The timer duration is calculated based on the
2704 * current vrate. vtime and hweight changes can make it too short
2705 * or too long. Each wait entry records the absolute cost it's
2706 * waiting for to allow re-evaluation using a custom wait entry.
2707 *
2708 * If too short, the timer simply reschedules itself. If too long,
2709 * the period timer will notice and trigger wakeups.
2710 *
2711 * All waiters are on iocg->waitq and the wait states are
2712 * synchronized using waitq.lock.
2713 */
2714 init_waitqueue_func_entry(&wait.wait, iocg_wake_fn);
2715 wait.wait.private = current;
2716 wait.bio = bio;
2717 wait.abs_cost = abs_cost;
2718 wait.committed = false; /* will be set true by waker */
2719
2720 __add_wait_queue_entry_tail(&iocg->waitq, &wait.wait);
2721 iocg_kick_waitq(iocg, ioc_locked, &now);
2722
2723 iocg_unlock(iocg, ioc_locked, &flags);
2724
2725 while (true) {
2726 set_current_state(TASK_UNINTERRUPTIBLE);
2727 if (wait.committed)
2728 break;
2729 io_schedule();
2730 }
2731
2732 /* waker already committed us, proceed */
2733 finish_wait(&iocg->waitq, &wait.wait);
2734 }
2735
2736 static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
2737 struct bio *bio)
2738 {
2739 struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
2740 struct ioc *ioc = rqos_to_ioc(rqos);
2741 sector_t bio_end = bio_end_sector(bio);
2742 struct ioc_now now;
2743 u64 vtime, abs_cost, cost;
2744 unsigned long flags;
2745
2746 /* bypass if disabled, still initializing, or for root cgroup */
2747 if (!ioc->enabled || !iocg || !iocg->level)
2748 return;
2749
2750 abs_cost = calc_vtime_cost(bio, iocg, true);
2751 if (!abs_cost)
2752 return;
2753
2754 ioc_now(ioc, &now);
2755
2756 vtime = atomic64_read(&iocg->vtime);
2757 cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now);
2758
2759 /* update cursor if backmerging into the request at the cursor */
2760 if (blk_rq_pos(rq) < bio_end &&
2761 blk_rq_pos(rq) + blk_rq_sectors(rq) == iocg->cursor)
2762 iocg->cursor = bio_end;
2763
2764 /*
2765 * Charge if there's enough vtime budget and the existing request has
2766 * cost assigned.
2767 */
2768 if (rq->bio && rq->bio->bi_iocost_cost &&
2769 time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow)) {
2770 iocg_commit_bio(iocg, bio, abs_cost, cost);
2771 return;
2772 }
2773
2774 /*
2775 * Otherwise, account it as debt if @iocg is online, which it should
2776 * be for the vast majority of cases. See debt handling in
2777 * ioc_rqos_throttle() for details.
2778 */
2779 spin_lock_irqsave(&ioc->lock, flags);
2780 spin_lock(&iocg->waitq.lock);
2781
2782 if (likely(!list_empty(&iocg->active_list))) {
2783 iocg_incur_debt(iocg, abs_cost, &now);
2784 if (iocg_kick_delay(iocg, &now))
2785 blkcg_schedule_throttle(rqos->disk,
2786 (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
2787 } else {
2788 iocg_commit_bio(iocg, bio, abs_cost, cost);
2789 }
2790
2791 spin_unlock(&iocg->waitq.lock);
2792 spin_unlock_irqrestore(&ioc->lock, flags);
2793 }
2794
2795 static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)
2796 {
2797 struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
2798
2799 if (iocg && bio->bi_iocost_cost)
2800 atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime);
2801 }
2802
2803 static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
2804 {
2805 struct ioc *ioc = rqos_to_ioc(rqos);
2806 struct ioc_pcpu_stat *ccs;
2807 u64 on_q_ns, rq_wait_ns, size_nsec;
2808 int pidx, rw;
2809
2810 if (!ioc->enabled || !rq->alloc_time_ns || !rq->start_time_ns)
2811 return;
2812
2813 switch (req_op(rq)) {
2814 case REQ_OP_READ:
2815 pidx = QOS_RLAT;
2816 rw = READ;
2817 break;
2818 case REQ_OP_WRITE:
2819 pidx = QOS_WLAT;
2820 rw = WRITE;
2821 break;
2822 default:
2823 return;
2824 }
2825
2826 on_q_ns = blk_time_get_ns() - rq->alloc_time_ns;
2827 rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns;
2828 size_nsec = div64_u64(calc_size_vtime_cost(rq, ioc), VTIME_PER_NSEC);
2829
2830 ccs = get_cpu_ptr(ioc->pcpu_stat);
2831
2832 if (on_q_ns <= size_nsec ||
2833 on_q_ns - size_nsec <= ioc->params.qos[pidx] * NSEC_PER_USEC)
2834 local_inc(&ccs->missed[rw].nr_met);
2835 else
2836 local_inc(&ccs->missed[rw].nr_missed);
2837
2838 local64_add(rq_wait_ns, &ccs->rq_wait_ns);
2839
2840 put_cpu_ptr(ccs);
2841 }
2842
2843 static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos)
2844 {
2845 struct ioc *ioc = rqos_to_ioc(rqos);
2846
2847 spin_lock_irq(&ioc->lock);
2848 ioc_refresh_params(ioc, false);
2849 spin_unlock_irq(&ioc->lock);
2850 }
2851
2852 static void ioc_rqos_exit(struct rq_qos *rqos)
2853 {
2854 struct ioc *ioc = rqos_to_ioc(rqos);
2855
2856 blkcg_deactivate_policy(rqos->disk, &blkcg_policy_iocost);
2857
2858 spin_lock_irq(&ioc->lock);
2859 ioc->running = IOC_STOP;
2860 spin_unlock_irq(&ioc->lock);
2861
2862 timer_shutdown_sync(&ioc->timer);
2863 free_percpu(ioc->pcpu_stat);
2864 kfree(ioc);
2865 }
2866
2867 static const struct rq_qos_ops ioc_rqos_ops = {
2868 .throttle = ioc_rqos_throttle,
2869 .merge = ioc_rqos_merge,
2870 .done_bio = ioc_rqos_done_bio,
2871 .done = ioc_rqos_done,
2872 .queue_depth_changed = ioc_rqos_queue_depth_changed,
2873 .exit = ioc_rqos_exit,
2874 };
2875
2876 static int blk_iocost_init(struct gendisk *disk)
2877 {
2878 struct ioc *ioc;
2879 int i, cpu, ret;
2880
2881 ioc = kzalloc(sizeof(*ioc), GFP_KERNEL);
2882 if (!ioc)
2883 return -ENOMEM;
2884
2885 ioc->pcpu_stat = alloc_percpu(struct ioc_pcpu_stat);
2886 if (!ioc->pcpu_stat) {
2887 kfree(ioc);
2888 return -ENOMEM;
2889 }
2890
2891 for_each_possible_cpu(cpu) {
2892 struct ioc_pcpu_stat *ccs = per_cpu_ptr(ioc->pcpu_stat, cpu);
2893
2894 for (i = 0; i < ARRAY_SIZE(ccs->missed); i++) {
2895 local_set(&ccs->missed[i].nr_met, 0);
2896 local_set(&ccs->missed[i].nr_missed, 0);
2897 }
2898 local64_set(&ccs->rq_wait_ns, 0);
2899 }
2900
2901 spin_lock_init(&ioc->lock);
2902 timer_setup(&ioc->timer, ioc_timer_fn, 0);
2903 INIT_LIST_HEAD(&ioc->active_iocgs);
2904
2905 ioc->running = IOC_IDLE;
2906 ioc->vtime_base_rate = VTIME_PER_USEC;
2907 atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);
2908 seqcount_spinlock_init(&ioc->period_seqcount, &ioc->lock);
2909 ioc->period_at = ktime_to_us(blk_time_get());
2910 atomic64_set(&ioc->cur_period, 0);
2911 atomic_set(&ioc->hweight_gen, 0);
2912
2913 spin_lock_irq(&ioc->lock);
2914 ioc->autop_idx = AUTOP_INVALID;
2915 ioc_refresh_params_disk(ioc, true, disk);
2916 spin_unlock_irq(&ioc->lock);
2917
2918 /*
2919 * rqos must be added before activation to allow ioc_pd_init() to
2920 * lookup the ioc from q. This means that the rqos methods may get
2921 * called before policy activation completion, can't assume that the
2922 * target bio has an iocg associated and need to test for NULL iocg.
2923 */
2924 ret = rq_qos_add(&ioc->rqos, disk, RQ_QOS_COST, &ioc_rqos_ops);
2925 if (ret)
2926 goto err_free_ioc;
2927
2928 ret = blkcg_activate_policy(disk, &blkcg_policy_iocost);
2929 if (ret)
2930 goto err_del_qos;
2931 return 0;
2932
2933 err_del_qos:
2934 rq_qos_del(&ioc->rqos);
2935 err_free_ioc:
2936 free_percpu(ioc->pcpu_stat);
2937 kfree(ioc);
2938 return ret;
2939 }
2940
2941 static struct blkcg_policy_data *ioc_cpd_alloc(gfp_t gfp)
2942 {
2943 struct ioc_cgrp *iocc;
2944
2945 iocc = kzalloc(sizeof(struct ioc_cgrp), gfp);
2946 if (!iocc)
2947 return NULL;
2948
2949 iocc->dfl_weight = CGROUP_WEIGHT_DFL * WEIGHT_ONE;
2950 return &iocc->cpd;
2951 }
2952
2953 static void ioc_cpd_free(struct blkcg_policy_data *cpd)
2954 {
2955 kfree(container_of(cpd, struct ioc_cgrp, cpd));
2956 }
2957
2958 static struct blkg_policy_data *ioc_pd_alloc(struct gendisk *disk,
2959 struct blkcg *blkcg, gfp_t gfp)
2960 {
2961 int levels = blkcg->css.cgroup->level + 1;
2962 struct ioc_gq *iocg;
2963
2964 iocg = kzalloc_node(struct_size(iocg, ancestors, levels), gfp,
2965 disk->node_id);
2966 if (!iocg)
2967 return NULL;
2968
2969 iocg->pcpu_stat = alloc_percpu_gfp(struct iocg_pcpu_stat, gfp);
2970 if (!iocg->pcpu_stat) {
2971 kfree(iocg);
2972 return NULL;
2973 }
2974
2975 return &iocg->pd;
2976 }
2977
2978 static void ioc_pd_init(struct blkg_policy_data *pd)
2979 {
2980 struct ioc_gq *iocg = pd_to_iocg(pd);
2981 struct blkcg_gq *blkg = pd_to_blkg(&iocg->pd);
2982 struct ioc *ioc = q_to_ioc(blkg->q);
2983 struct ioc_now now;
2984 struct blkcg_gq *tblkg;
2985 unsigned long flags;
2986
2987 ioc_now(ioc, &now);
2988
2989 iocg->ioc = ioc;
2990 atomic64_set(&iocg->vtime, now.vnow);
2991 atomic64_set(&iocg->done_vtime, now.vnow);
2992 atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period));
2993 INIT_LIST_HEAD(&iocg->active_list);
2994 INIT_LIST_HEAD(&iocg->walk_list);
2995 INIT_LIST_HEAD(&iocg->surplus_list);
2996 iocg->hweight_active = WEIGHT_ONE;
2997 iocg->hweight_inuse = WEIGHT_ONE;
2998
2999 init_waitqueue_head(&iocg->waitq);
3000 hrtimer_init(&iocg->waitq_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
3001 iocg->waitq_timer.function = iocg_waitq_timer_fn;
3002
3003 iocg->level = blkg->blkcg->css.cgroup->level;
3004
3005 for (tblkg = blkg; tblkg; tblkg = tblkg->parent) {
3006 struct ioc_gq *tiocg = blkg_to_iocg(tblkg);
3007 iocg->ancestors[tiocg->level] = tiocg;
3008 }
3009
3010 spin_lock_irqsave(&ioc->lock, flags);
3011 weight_updated(iocg, &now);
3012 spin_unlock_irqrestore(&ioc->lock, flags);
3013 }
3014
3015 static void ioc_pd_free(struct blkg_policy_data *pd)
3016 {
3017 struct ioc_gq *iocg = pd_to_iocg(pd);
3018 struct ioc *ioc = iocg->ioc;
3019 unsigned long flags;
3020
3021 if (ioc) {
3022 spin_lock_irqsave(&ioc->lock, flags);
3023
3024 if (!list_empty(&iocg->active_list)) {
3025 struct ioc_now now;
3026
3027 ioc_now(ioc, &now);
3028 propagate_weights(iocg, 0, 0, false, &now);
3029 list_del_init(&iocg->active_list);
3030 }
3031
3032 WARN_ON_ONCE(!list_empty(&iocg->walk_list));
3033 WARN_ON_ONCE(!list_empty(&iocg->surplus_list));
3034
3035 spin_unlock_irqrestore(&ioc->lock, flags);
3036
3037 hrtimer_cancel(&iocg->waitq_timer);
3038 }
3039 free_percpu(iocg->pcpu_stat);
3040 kfree(iocg);
3041 }
3042
3043 static void ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
3044 {
3045 struct ioc_gq *iocg = pd_to_iocg(pd);
3046 struct ioc *ioc = iocg->ioc;
3047
3048 if (!ioc->enabled)
3049 return;
3050
3051 if (iocg->level == 0) {
3052 unsigned vp10k = DIV64_U64_ROUND_CLOSEST(
3053 ioc->vtime_base_rate * 10000,
3054 VTIME_PER_USEC);
3055 seq_printf(s, " cost.vrate=%u.%02u", vp10k / 100, vp10k % 100);
3056 }
3057
3058 seq_printf(s, " cost.usage=%llu", iocg->last_stat.usage_us);
3059
3060 if (blkcg_debug_stats)
3061 seq_printf(s, " cost.wait=%llu cost.indebt=%llu cost.indelay=%llu",
3062 iocg->last_stat.wait_us,
3063 iocg->last_stat.indebt_us,
3064 iocg->last_stat.indelay_us);
3065 }
3066
3067 static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
3068 int off)
3069 {
3070 const char *dname = blkg_dev_name(pd->blkg);
3071 struct ioc_gq *iocg = pd_to_iocg(pd);
3072
3073 if (dname && iocg->cfg_weight)
3074 seq_printf(sf, "%s %u\n", dname, iocg->cfg_weight / WEIGHT_ONE);
3075 return 0;
3076 }
3077
3078
3079 static int ioc_weight_show(struct seq_file *sf, void *v)
3080 {
3081 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
3082 struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
3083
3084 seq_printf(sf, "default %u\n", iocc->dfl_weight / WEIGHT_ONE);
3085 blkcg_print_blkgs(sf, blkcg, ioc_weight_prfill,
3086 &blkcg_policy_iocost, seq_cft(sf)->private, false);
3087 return 0;
3088 }
3089
3090 static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
3091 size_t nbytes, loff_t off)
3092 {
3093 struct blkcg *blkcg = css_to_blkcg(of_css(of));
3094 struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
3095 struct blkg_conf_ctx ctx;
3096 struct ioc_now now;
3097 struct ioc_gq *iocg;
3098 u32 v;
3099 int ret;
3100
3101 if (!strchr(buf, ':')) {
3102 struct blkcg_gq *blkg;
3103
3104 if (!sscanf(buf, "default %u", &v) && !sscanf(buf, "%u", &v))
3105 return -EINVAL;
3106
3107 if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
3108 return -EINVAL;
3109
3110 spin_lock_irq(&blkcg->lock);
3111 iocc->dfl_weight = v * WEIGHT_ONE;
3112 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
3113 struct ioc_gq *iocg = blkg_to_iocg(blkg);
3114
3115 if (iocg) {
3116 spin_lock(&iocg->ioc->lock);
3117 ioc_now(iocg->ioc, &now);
3118 weight_updated(iocg, &now);
3119 spin_unlock(&iocg->ioc->lock);
3120 }
3121 }
3122 spin_unlock_irq(&blkcg->lock);
3123
3124 return nbytes;
3125 }
3126
3127 blkg_conf_init(&ctx, buf);
3128
3129 ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, &ctx);
3130 if (ret)
3131 goto err;
3132
3133 iocg = blkg_to_iocg(ctx.blkg);
3134
3135 if (!strncmp(ctx.body, "default", 7)) {
3136 v = 0;
3137 } else {
3138 if (!sscanf(ctx.body, "%u", &v))
3139 goto einval;
3140 if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
3141 goto einval;
3142 }
3143
3144 spin_lock(&iocg->ioc->lock);
3145 iocg->cfg_weight = v * WEIGHT_ONE;
3146 ioc_now(iocg->ioc, &now);
3147 weight_updated(iocg, &now);
3148 spin_unlock(&iocg->ioc->lock);
3149
3150 blkg_conf_exit(&ctx);
3151 return nbytes;
3152
3153 einval:
3154 ret = -EINVAL;
3155 err:
3156 blkg_conf_exit(&ctx);
3157 return ret;
3158 }
3159
3160 static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
3161 int off)
3162 {
3163 const char *dname = blkg_dev_name(pd->blkg);
3164 struct ioc *ioc = pd_to_iocg(pd)->ioc;
3165
3166 if (!dname)
3167 return 0;
3168
3169 spin_lock_irq(&ioc->lock);
3170 seq_printf(sf, "%s enable=%d ctrl=%s rpct=%u.%02u rlat=%u wpct=%u.%02u wlat=%u min=%u.%02u max=%u.%02u\n",
3171 dname, ioc->enabled, ioc->user_qos_params ? "user" : "auto",
3172 ioc->params.qos[QOS_RPPM] / 10000,
3173 ioc->params.qos[QOS_RPPM] % 10000 / 100,
3174 ioc->params.qos[QOS_RLAT],
3175 ioc->params.qos[QOS_WPPM] / 10000,
3176 ioc->params.qos[QOS_WPPM] % 10000 / 100,
3177 ioc->params.qos[QOS_WLAT],
3178 ioc->params.qos[QOS_MIN] / 10000,
3179 ioc->params.qos[QOS_MIN] % 10000 / 100,
3180 ioc->params.qos[QOS_MAX] / 10000,
3181 ioc->params.qos[QOS_MAX] % 10000 / 100);
3182 spin_unlock_irq(&ioc->lock);
3183 return 0;
3184 }
3185
3186 static int ioc_qos_show(struct seq_file *sf, void *v)
3187 {
3188 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
3189
3190 blkcg_print_blkgs(sf, blkcg, ioc_qos_prfill,
3191 &blkcg_policy_iocost, seq_cft(sf)->private, false);
3192 return 0;
3193 }
3194
3195 static const match_table_t qos_ctrl_tokens = {
3196 { QOS_ENABLE, "enable=%u" },
3197 { QOS_CTRL, "ctrl=%s" },
3198 { NR_QOS_CTRL_PARAMS, NULL },
3199 };
3200
3201 static const match_table_t qos_tokens = {
3202 { QOS_RPPM, "rpct=%s" },
3203 { QOS_RLAT, "rlat=%u" },
3204 { QOS_WPPM, "wpct=%s" },
3205 { QOS_WLAT, "wlat=%u" },
3206 { QOS_MIN, "min=%s" },
3207 { QOS_MAX, "max=%s" },
3208 { NR_QOS_PARAMS, NULL },
3209 };
3210
3211 static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
3212 size_t nbytes, loff_t off)
3213 {
3214 struct blkg_conf_ctx ctx;
3215 struct gendisk *disk;
3216 struct ioc *ioc;
3217 u32 qos[NR_QOS_PARAMS];
3218 bool enable, user;
3219 char *body, *p;
3220 int ret;
3221
3222 blkg_conf_init(&ctx, input);
3223
3224 ret = blkg_conf_open_bdev(&ctx);
3225 if (ret)
3226 goto err;
3227
3228 body = ctx.body;
3229 disk = ctx.bdev->bd_disk;
3230 if (!queue_is_mq(disk->queue)) {
3231 ret = -EOPNOTSUPP;
3232 goto err;
3233 }
3234
3235 ioc = q_to_ioc(disk->queue);
3236 if (!ioc) {
3237 ret = blk_iocost_init(disk);
3238 if (ret)
3239 goto err;
3240 ioc = q_to_ioc(disk->queue);
3241 }
3242
3243 blk_mq_freeze_queue(disk->queue);
3244 blk_mq_quiesce_queue(disk->queue);
3245
3246 spin_lock_irq(&ioc->lock);
3247 memcpy(qos, ioc->params.qos, sizeof(qos));
3248 enable = ioc->enabled;
3249 user = ioc->user_qos_params;
3250
3251 while ((p = strsep(&body, " \t\n"))) {
3252 substring_t args[MAX_OPT_ARGS];
3253 char buf[32];
3254 int tok;
3255 s64 v;
3256
3257 if (!*p)
3258 continue;
3259
3260 switch (match_token(p, qos_ctrl_tokens, args)) {
3261 case QOS_ENABLE:
3262 if (match_u64(&args[0], &v))
3263 goto einval;
3264 enable = v;
3265 continue;
3266 case QOS_CTRL:
3267 match_strlcpy(buf, &args[0], sizeof(buf));
3268 if (!strcmp(buf, "auto"))
3269 user = false;
3270 else if (!strcmp(buf, "user"))
3271 user = true;
3272 else
3273 goto einval;
3274 continue;
3275 }
3276
3277 tok = match_token(p, qos_tokens, args);
3278 switch (tok) {
3279 case QOS_RPPM:
3280 case QOS_WPPM:
3281 if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
3282 sizeof(buf))
3283 goto einval;
3284 if (cgroup_parse_float(buf, 2, &v))
3285 goto einval;
3286 if (v < 0 || v > 10000)
3287 goto einval;
3288 qos[tok] = v * 100;
3289 break;
3290 case QOS_RLAT:
3291 case QOS_WLAT:
3292 if (match_u64(&args[0], &v))
3293 goto einval;
3294 qos[tok] = v;
3295 break;
3296 case QOS_MIN:
3297 case QOS_MAX:
3298 if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
3299 sizeof(buf))
3300 goto einval;
3301 if (cgroup_parse_float(buf, 2, &v))
3302 goto einval;
3303 if (v < 0)
3304 goto einval;
3305 qos[tok] = clamp_t(s64, v * 100,
3306 VRATE_MIN_PPM, VRATE_MAX_PPM);
3307 break;
3308 default:
3309 goto einval;
3310 }
3311 user = true;
3312 }
3313
3314 if (qos[QOS_MIN] > qos[QOS_MAX])
3315 goto einval;
3316
3317 if (enable && !ioc->enabled) {
3318 blk_stat_enable_accounting(disk->queue);
3319 blk_queue_flag_set(QUEUE_FLAG_RQ_ALLOC_TIME, disk->queue);
3320 ioc->enabled = true;
3321 } else if (!enable && ioc->enabled) {
3322 blk_stat_disable_accounting(disk->queue);
3323 blk_queue_flag_clear(QUEUE_FLAG_RQ_ALLOC_TIME, disk->queue);
3324 ioc->enabled = false;
3325 }
3326
3327 if (user) {
3328 memcpy(ioc->params.qos, qos, sizeof(qos));
3329 ioc->user_qos_params = true;
3330 } else {
3331 ioc->user_qos_params = false;
3332 }
3333
3334 ioc_refresh_params(ioc, true);
3335 spin_unlock_irq(&ioc->lock);
3336
3337 if (enable)
3338 wbt_disable_default(disk);
3339 else
3340 wbt_enable_default(disk);
3341
3342 blk_mq_unquiesce_queue(disk->queue);
3343 blk_mq_unfreeze_queue(disk->queue);
3344
3345 blkg_conf_exit(&ctx);
3346 return nbytes;
3347 einval:
3348 spin_unlock_irq(&ioc->lock);
3349
3350 blk_mq_unquiesce_queue(disk->queue);
3351 blk_mq_unfreeze_queue(disk->queue);
3352
3353 ret = -EINVAL;
3354 err:
3355 blkg_conf_exit(&ctx);
3356 return ret;
3357 }
3358
3359 static u64 ioc_cost_model_prfill(struct seq_file *sf,
3360 struct blkg_policy_data *pd, int off)
3361 {
3362 const char *dname = blkg_dev_name(pd->blkg);
3363 struct ioc *ioc = pd_to_iocg(pd)->ioc;
3364 u64 *u = ioc->params.i_lcoefs;
3365
3366 if (!dname)
3367 return 0;
3368
3369 spin_lock_irq(&ioc->lock);
3370 seq_printf(sf, "%s ctrl=%s model=linear "
3371 "rbps=%llu rseqiops=%llu rrandiops=%llu "
3372 "wbps=%llu wseqiops=%llu wrandiops=%llu\n",
3373 dname, ioc->user_cost_model ? "user" : "auto",
3374 u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
3375 u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS]);
3376 spin_unlock_irq(&ioc->lock);
3377 return 0;
3378 }
3379
3380 static int ioc_cost_model_show(struct seq_file *sf, void *v)
3381 {
3382 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
3383
3384 blkcg_print_blkgs(sf, blkcg, ioc_cost_model_prfill,
3385 &blkcg_policy_iocost, seq_cft(sf)->private, false);
3386 return 0;
3387 }
3388
3389 static const match_table_t cost_ctrl_tokens = {
3390 { COST_CTRL, "ctrl=%s" },
3391 { COST_MODEL, "model=%s" },
3392 { NR_COST_CTRL_PARAMS, NULL },
3393 };
3394
3395 static const match_table_t i_lcoef_tokens = {
3396 { I_LCOEF_RBPS, "rbps=%u" },
3397 { I_LCOEF_RSEQIOPS, "rseqiops=%u" },
3398 { I_LCOEF_RRANDIOPS, "rrandiops=%u" },
3399 { I_LCOEF_WBPS, "wbps=%u" },
3400 { I_LCOEF_WSEQIOPS, "wseqiops=%u" },
3401 { I_LCOEF_WRANDIOPS, "wrandiops=%u" },
3402 { NR_I_LCOEFS, NULL },
3403 };
3404
3405 static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
3406 size_t nbytes, loff_t off)
3407 {
3408 struct blkg_conf_ctx ctx;
3409 struct request_queue *q;
3410 struct ioc *ioc;
3411 u64 u[NR_I_LCOEFS];
3412 bool user;
3413 char *body, *p;
3414 int ret;
3415
3416 blkg_conf_init(&ctx, input);
3417
3418 ret = blkg_conf_open_bdev(&ctx);
3419 if (ret)
3420 goto err;
3421
3422 body = ctx.body;
3423 q = bdev_get_queue(ctx.bdev);
3424 if (!queue_is_mq(q)) {
3425 ret = -EOPNOTSUPP;
3426 goto err;
3427 }
3428
3429 ioc = q_to_ioc(q);
3430 if (!ioc) {
3431 ret = blk_iocost_init(ctx.bdev->bd_disk);
3432 if (ret)
3433 goto err;
3434 ioc = q_to_ioc(q);
3435 }
3436
3437 blk_mq_freeze_queue(q);
3438 blk_mq_quiesce_queue(q);
3439
3440 spin_lock_irq(&ioc->lock);
3441 memcpy(u, ioc->params.i_lcoefs, sizeof(u));
3442 user = ioc->user_cost_model;
3443
3444 while ((p = strsep(&body, " \t\n"))) {
3445 substring_t args[MAX_OPT_ARGS];
3446 char buf[32];
3447 int tok;
3448 u64 v;
3449
3450 if (!*p)
3451 continue;
3452
3453 switch (match_token(p, cost_ctrl_tokens, args)) {
3454 case COST_CTRL:
3455 match_strlcpy(buf, &args[0], sizeof(buf));
3456 if (!strcmp(buf, "auto"))
3457 user = false;
3458 else if (!strcmp(buf, "user"))
3459 user = true;
3460 else
3461 goto einval;
3462 continue;
3463 case COST_MODEL:
3464 match_strlcpy(buf, &args[0], sizeof(buf));
3465 if (strcmp(buf, "linear"))
3466 goto einval;
3467 continue;
3468 }
3469
3470 tok = match_token(p, i_lcoef_tokens, args);
3471 if (tok == NR_I_LCOEFS)
3472 goto einval;
3473 if (match_u64(&args[0], &v))
3474 goto einval;
3475 u[tok] = v;
3476 user = true;
3477 }
3478
3479 if (user) {
3480 memcpy(ioc->params.i_lcoefs, u, sizeof(u));
3481 ioc->user_cost_model = true;
3482 } else {
3483 ioc->user_cost_model = false;
3484 }
3485 ioc_refresh_params(ioc, true);
3486 spin_unlock_irq(&ioc->lock);
3487
3488 blk_mq_unquiesce_queue(q);
3489 blk_mq_unfreeze_queue(q);
3490
3491 blkg_conf_exit(&ctx);
3492 return nbytes;
3493
3494 einval:
3495 spin_unlock_irq(&ioc->lock);
3496
3497 blk_mq_unquiesce_queue(q);
3498 blk_mq_unfreeze_queue(q);
3499
3500 ret = -EINVAL;
3501 err:
3502 blkg_conf_exit(&ctx);
3503 return ret;
3504 }
3505
3506 static struct cftype ioc_files[] = {
3507 {
3508 .name = "weight",
3509 .flags = CFTYPE_NOT_ON_ROOT,
3510 .seq_show = ioc_weight_show,
3511 .write = ioc_weight_write,
3512 },
3513 {
3514 .name = "cost.qos",
3515 .flags = CFTYPE_ONLY_ON_ROOT,
3516 .seq_show = ioc_qos_show,
3517 .write = ioc_qos_write,
3518 },
3519 {
3520 .name = "cost.model",
3521 .flags = CFTYPE_ONLY_ON_ROOT,
3522 .seq_show = ioc_cost_model_show,
3523 .write = ioc_cost_model_write,
3524 },
3525 {}
3526 };
3527
3528 static struct blkcg_policy blkcg_policy_iocost = {
3529 .dfl_cftypes = ioc_files,
3530 .cpd_alloc_fn = ioc_cpd_alloc,
3531 .cpd_free_fn = ioc_cpd_free,
3532 .pd_alloc_fn = ioc_pd_alloc,
3533 .pd_init_fn = ioc_pd_init,
3534 .pd_free_fn = ioc_pd_free,
3535 .pd_stat_fn = ioc_pd_stat,
3536 };
3537
3538 static int __init ioc_init(void)
3539 {
3540 return blkcg_policy_register(&blkcg_policy_iocost);
3541 }
3542
3543 static void __exit ioc_exit(void)
3544 {
3545 blkcg_policy_unregister(&blkcg_policy_iocost);
3546 }
3547
3548 module_init(ioc_init);
3549 module_exit(ioc_exit);
3550
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