1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ========================== 3 ==========================
4 RCU Torture Test Operation 4 RCU Torture Test Operation
5 ========================== 5 ==========================
6 6
7 7
8 CONFIG_RCU_TORTURE_TEST 8 CONFIG_RCU_TORTURE_TEST
9 ======================= 9 =======================
10 10
11 The CONFIG_RCU_TORTURE_TEST config option is a 11 The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
12 implementations. It creates an rcutorture ker 12 implementations. It creates an rcutorture kernel module that can
13 be loaded to run a torture test. The test per 13 be loaded to run a torture test. The test periodically outputs
14 status messages via printk(), which can be exa 14 status messages via printk(), which can be examined via the dmesg
15 command (perhaps grepping for "torture"). The 15 command (perhaps grepping for "torture"). The test is started
16 when the module is loaded, and stops when the 16 when the module is loaded, and stops when the module is unloaded.
17 17
18 Module parameters are prefixed by "rcutorture. 18 Module parameters are prefixed by "rcutorture." in
19 Documentation/admin-guide/kernel-parameters.tx 19 Documentation/admin-guide/kernel-parameters.txt.
20 20
21 Output 21 Output
22 ====== 22 ======
23 23
24 The statistics output is as follows:: 24 The statistics output is as follows::
25 25
26 rcu-torture:--- Start of test: nreader 26 rcu-torture:--- Start of test: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
27 rcu-torture: rtc: (null) ver 27 rcu-torture: rtc: (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
28 rcu-torture: Reader Pipe: 727860534 3 28 rcu-torture: Reader Pipe: 727860534 34213 0 0 0 0 0 0 0 0 0
29 rcu-torture: Reader Batch: 727877838 29 rcu-torture: Reader Batch: 727877838 17003 0 0 0 0 0 0 0 0 0
30 rcu-torture: Free-Block Circulation: 30 rcu-torture: Free-Block Circulation: 155440 155440 155440 155440 155440 155440 155440 155440 155440 155440 0
31 rcu-torture:--- End of test: SUCCESS: 31 rcu-torture:--- End of test: SUCCESS: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
32 32
33 The command "dmesg | grep torture:" will extra 33 The command "dmesg | grep torture:" will extract this information on
34 most systems. On more esoteric configurations 34 most systems. On more esoteric configurations, it may be necessary to
35 use other commands to access the output of the 35 use other commands to access the output of the printk()s used by
36 the RCU torture test. The printk()s use KERN_ 36 the RCU torture test. The printk()s use KERN_ALERT, so they should
37 be evident. ;-) 37 be evident. ;-)
38 38
39 The first and last lines show the rcutorture m 39 The first and last lines show the rcutorture module parameters, and the
40 last line shows either "SUCCESS" or "FAILURE", 40 last line shows either "SUCCESS" or "FAILURE", based on rcutorture's
41 automatic determination as to whether RCU oper 41 automatic determination as to whether RCU operated correctly.
42 42
43 The entries are as follows: 43 The entries are as follows:
44 44
45 * "rtc": The hexadecimal address of the 45 * "rtc": The hexadecimal address of the structure currently visible
46 to readers. 46 to readers.
47 47
48 * "ver": The number of times since boot 48 * "ver": The number of times since boot that the RCU writer task
49 has changed the structure visible to r 49 has changed the structure visible to readers.
50 50
51 * "tfle": If non-zero, indicates that th 51 * "tfle": If non-zero, indicates that the "torture freelist"
52 containing structures to be placed int 52 containing structures to be placed into the "rtc" area is empty.
53 This condition is important, since it 53 This condition is important, since it can fool you into thinking
54 that RCU is working when it is not. : 54 that RCU is working when it is not. :-/
55 55
56 * "rta": Number of structures allocated 56 * "rta": Number of structures allocated from the torture freelist.
57 57
58 * "rtaf": Number of allocations from the 58 * "rtaf": Number of allocations from the torture freelist that have
59 failed due to the list being empty. I 59 failed due to the list being empty. It is not unusual for this
60 to be non-zero, but it is bad for it t 60 to be non-zero, but it is bad for it to be a large fraction of
61 the value indicated by "rta". 61 the value indicated by "rta".
62 62
63 * "rtf": Number of frees into the tortur 63 * "rtf": Number of frees into the torture freelist.
64 64
65 * "rtmbe": A non-zero value indicates th 65 * "rtmbe": A non-zero value indicates that rcutorture believes that
66 rcu_assign_pointer() and rcu_dereferen 66 rcu_assign_pointer() and rcu_dereference() are not working
67 correctly. This value should be zero. 67 correctly. This value should be zero.
68 68
69 * "rtbe": A non-zero value indicates tha 69 * "rtbe": A non-zero value indicates that one of the rcu_barrier()
70 family of functions is not working cor 70 family of functions is not working correctly.
71 71
72 * "rtbke": rcutorture was unable to crea 72 * "rtbke": rcutorture was unable to create the real-time kthreads
73 used to force RCU priority inversion. 73 used to force RCU priority inversion. This value should be zero.
74 74
75 * "rtbre": Although rcutorture successfu 75 * "rtbre": Although rcutorture successfully created the kthreads
76 used to force RCU priority inversion, 76 used to force RCU priority inversion, it was unable to set them
77 to the real-time priority level of 1. 77 to the real-time priority level of 1. This value should be zero.
78 78
79 * "rtbf": The number of times that RCU p 79 * "rtbf": The number of times that RCU priority boosting failed
80 to resolve RCU priority inversion. 80 to resolve RCU priority inversion.
81 81
82 * "rtb": The number of times that rcutor 82 * "rtb": The number of times that rcutorture attempted to force
83 an RCU priority inversion condition. 83 an RCU priority inversion condition. If you are testing RCU
84 priority boosting via the "test_boost" 84 priority boosting via the "test_boost" module parameter, this
85 value should be non-zero. 85 value should be non-zero.
86 86
87 * "nt": The number of times rcutorture r 87 * "nt": The number of times rcutorture ran RCU read-side code from
88 within a timer handler. This value sh 88 within a timer handler. This value should be non-zero only
89 if you specified the "irqreader" modul 89 if you specified the "irqreader" module parameter.
90 90
91 * "Reader Pipe": Histogram of "ages" of 91 * "Reader Pipe": Histogram of "ages" of structures seen by readers.
92 If any entries past the first two are 92 If any entries past the first two are non-zero, RCU is broken.
93 And rcutorture prints the error flag s 93 And rcutorture prints the error flag string "!!!" to make sure
94 you notice. The age of a newly alloca 94 you notice. The age of a newly allocated structure is zero,
95 it becomes one when removed from reade 95 it becomes one when removed from reader visibility, and is
96 incremented once per grace period subs 96 incremented once per grace period subsequently -- and is freed
97 after passing through (RCU_TORTURE_PIP 97 after passing through (RCU_TORTURE_PIPE_LEN-2) grace periods.
98 98
99 The output displayed above was taken f 99 The output displayed above was taken from a correctly working
100 RCU. If you want to see what it looks 100 RCU. If you want to see what it looks like when broken, break
101 it yourself. ;-) 101 it yourself. ;-)
102 102
103 * "Reader Batch": Another histogram of " 103 * "Reader Batch": Another histogram of "ages" of structures seen
104 by readers, but in terms of counter fl 104 by readers, but in terms of counter flips (or batches) rather
105 than in terms of grace periods. The l 105 than in terms of grace periods. The legal number of non-zero
106 entries is again two. The reason for 106 entries is again two. The reason for this separate view is that
107 it is sometimes easier to get the thir 107 it is sometimes easier to get the third entry to show up in the
108 "Reader Batch" list than in the "Reade 108 "Reader Batch" list than in the "Reader Pipe" list.
109 109
110 * "Free-Block Circulation": Shows the nu 110 * "Free-Block Circulation": Shows the number of torture structures
111 that have reached a given point in the 111 that have reached a given point in the pipeline. The first element
112 should closely correspond to the numbe 112 should closely correspond to the number of structures allocated,
113 the second to the number that have bee 113 the second to the number that have been removed from reader view,
114 and all but the last remaining to the 114 and all but the last remaining to the corresponding number of
115 passes through a grace period. The la 115 passes through a grace period. The last entry should be zero,
116 as it is only incremented if a torture 116 as it is only incremented if a torture structure's counter
117 somehow gets incremented farther than 117 somehow gets incremented farther than it should.
118 118
119 Different implementations of RCU can provide i 119 Different implementations of RCU can provide implementation-specific
120 additional information. For example, Tree SRC 120 additional information. For example, Tree SRCU provides the following
121 additional line:: 121 additional line::
122 122
123 srcud-torture: Tree SRCU per-CPU(idx=0 123 srcud-torture: Tree SRCU per-CPU(idx=0): 0(35,-21) 1(-4,24) 2(1,1) 3(-26,20) 4(28,-47) 5(-9,4) 6(-10,14) 7(-14,11) T(1,6)
124 124
125 This line shows the per-CPU counter state, in 125 This line shows the per-CPU counter state, in this case for Tree SRCU
126 using a dynamically allocated srcu_struct (hen 126 using a dynamically allocated srcu_struct (hence "srcud-" rather than
127 "srcu-"). The numbers in parentheses are the 127 "srcu-"). The numbers in parentheses are the values of the "old" and
128 "current" counters for the corresponding CPU. 128 "current" counters for the corresponding CPU. The "idx" value maps the
129 "old" and "current" values to the underlying a 129 "old" and "current" values to the underlying array, and is useful for
130 debugging. The final "T" entry contains the t 130 debugging. The final "T" entry contains the totals of the counters.
131 131
132 Usage on Specific Kernel Builds 132 Usage on Specific Kernel Builds
133 =============================== 133 ===============================
134 134
135 It is sometimes desirable to torture RCU on a 135 It is sometimes desirable to torture RCU on a specific kernel build,
136 for example, when preparing to put that kernel 136 for example, when preparing to put that kernel build into production.
137 In that case, the kernel should be built with 137 In that case, the kernel should be built with CONFIG_RCU_TORTURE_TEST=m
138 so that the test can be started using modprobe 138 so that the test can be started using modprobe and terminated using rmmod.
139 139
140 For example, the following script may be used 140 For example, the following script may be used to torture RCU::
141 141
142 #!/bin/sh 142 #!/bin/sh
143 143
144 modprobe rcutorture 144 modprobe rcutorture
145 sleep 3600 145 sleep 3600
146 rmmod rcutorture 146 rmmod rcutorture
147 dmesg | grep torture: 147 dmesg | grep torture:
148 148
149 The output can be manually inspected for the e 149 The output can be manually inspected for the error flag of "!!!".
150 One could of course create a more elaborate sc 150 One could of course create a more elaborate script that automatically
151 checked for such errors. The "rmmod" command 151 checked for such errors. The "rmmod" command forces a "SUCCESS",
152 "FAILURE", or "RCU_HOTPLUG" indication to be p 152 "FAILURE", or "RCU_HOTPLUG" indication to be printk()ed. The first
153 two are self-explanatory, while the last indic 153 two are self-explanatory, while the last indicates that while there
154 were no RCU failures, CPU-hotplug problems wer 154 were no RCU failures, CPU-hotplug problems were detected.
155 155
156 156
157 Usage on Mainline Kernels 157 Usage on Mainline Kernels
158 ========================= 158 =========================
159 159
160 When using rcutorture to test changes to RCU i 160 When using rcutorture to test changes to RCU itself, it is often
161 necessary to build a number of kernels in orde 161 necessary to build a number of kernels in order to test that change
162 across a broad range of combinations of the re 162 across a broad range of combinations of the relevant Kconfig options
163 and of the relevant kernel boot parameters. I 163 and of the relevant kernel boot parameters. In this situation, use
164 of modprobe and rmmod can be quite time-consum 164 of modprobe and rmmod can be quite time-consuming and error-prone.
165 165
166 Therefore, the tools/testing/selftests/rcutort 166 Therefore, the tools/testing/selftests/rcutorture/bin/kvm.sh
167 script is available for mainline testing for x 167 script is available for mainline testing for x86, arm64, and
168 powerpc. By default, it will run the series o 168 powerpc. By default, it will run the series of tests specified by
169 tools/testing/selftests/rcutorture/configs/rcu 169 tools/testing/selftests/rcutorture/configs/rcu/CFLIST, with each test
170 running for 30 minutes within a guest OS using 170 running for 30 minutes within a guest OS using a minimal userspace
171 supplied by an automatically generated initrd. 171 supplied by an automatically generated initrd. After the tests are
172 complete, the resulting build products and con 172 complete, the resulting build products and console output are analyzed
173 for errors and the results of the runs are sum 173 for errors and the results of the runs are summarized.
174 174
175 On larger systems, rcutorture testing can be a 175 On larger systems, rcutorture testing can be accelerated by passing the
176 --cpus argument to kvm.sh. For example, on a 176 --cpus argument to kvm.sh. For example, on a 64-CPU system, "--cpus 43"
177 would use up to 43 CPUs to run tests concurren 177 would use up to 43 CPUs to run tests concurrently, which as of v5.4 would
178 complete all the scenarios in two batches, red 178 complete all the scenarios in two batches, reducing the time to complete
179 from about eight hours to about one hour (not 179 from about eight hours to about one hour (not counting the time to build
180 the sixteen kernels). The "--dryrun sched" ar 180 the sixteen kernels). The "--dryrun sched" argument will not run tests,
181 but rather tell you how the tests would be sch 181 but rather tell you how the tests would be scheduled into batches. This
182 can be useful when working out how many CPUs t 182 can be useful when working out how many CPUs to specify in the --cpus
183 argument. 183 argument.
184 184
185 Not all changes require that all scenarios be 185 Not all changes require that all scenarios be run. For example, a change
186 to Tree SRCU might run only the SRCU-N and SRC 186 to Tree SRCU might run only the SRCU-N and SRCU-P scenarios using the
187 --configs argument to kvm.sh as follows: "--c 187 --configs argument to kvm.sh as follows: "--configs 'SRCU-N SRCU-P'".
188 Large systems can run multiple copies of the f 188 Large systems can run multiple copies of the full set of scenarios,
189 for example, a system with 448 hardware thread 189 for example, a system with 448 hardware threads can run five instances
190 of the full set concurrently. To make this ha 190 of the full set concurrently. To make this happen::
191 191
192 kvm.sh --cpus 448 --configs '5*CFLIST' 192 kvm.sh --cpus 448 --configs '5*CFLIST'
193 193
194 Alternatively, such a system can run 56 concur 194 Alternatively, such a system can run 56 concurrent instances of a single
195 eight-CPU scenario:: 195 eight-CPU scenario::
196 196
197 kvm.sh --cpus 448 --configs '56*TREE04 197 kvm.sh --cpus 448 --configs '56*TREE04'
198 198
199 Or 28 concurrent instances of each of two eigh 199 Or 28 concurrent instances of each of two eight-CPU scenarios::
200 200
201 kvm.sh --cpus 448 --configs '28*TREE03 201 kvm.sh --cpus 448 --configs '28*TREE03 28*TREE04'
202 202
203 Of course, each concurrent instance will use m 203 Of course, each concurrent instance will use memory, which can be
204 limited using the --memory argument, which def 204 limited using the --memory argument, which defaults to 512M. Small
205 values for memory may require disabling the ca 205 values for memory may require disabling the callback-flooding tests
206 using the --bootargs parameter discussed below 206 using the --bootargs parameter discussed below.
207 207
208 Sometimes additional debugging is useful, and 208 Sometimes additional debugging is useful, and in such cases the --kconfig
209 parameter to kvm.sh may be used, for example, 209 parameter to kvm.sh may be used, for example, ``--kconfig 'CONFIG_RCU_EQS_DEBUG=y'``.
210 In addition, there are the --gdb, --kasan, and 210 In addition, there are the --gdb, --kasan, and --kcsan parameters.
211 Note that --gdb limits you to one scenario per 211 Note that --gdb limits you to one scenario per kvm.sh run and requires
212 that you have another window open from which t 212 that you have another window open from which to run ``gdb`` as instructed
213 by the script. 213 by the script.
214 214
215 Kernel boot arguments can also be supplied, fo 215 Kernel boot arguments can also be supplied, for example, to control
216 rcutorture's module parameters. For example, 216 rcutorture's module parameters. For example, to test a change to RCU's
217 CPU stall-warning code, use "--bootargs 'rcuto 217 CPU stall-warning code, use "--bootargs 'rcutorture.stall_cpu=30'".
218 This will of course result in the scripting re 218 This will of course result in the scripting reporting a failure, namely
219 the resulting RCU CPU stall warning. As noted 219 the resulting RCU CPU stall warning. As noted above, reducing memory may
220 require disabling rcutorture's callback-floodi 220 require disabling rcutorture's callback-flooding tests::
221 221
222 kvm.sh --cpus 448 --configs '56*TREE04 222 kvm.sh --cpus 448 --configs '56*TREE04' --memory 128M \
223 --bootargs 'rcutorture.fwd_pro 223 --bootargs 'rcutorture.fwd_progress=0'
224 224
225 Sometimes all that is needed is a full set of 225 Sometimes all that is needed is a full set of kernel builds. This is
226 what the --buildonly parameter does. 226 what the --buildonly parameter does.
227 227
228 The --duration parameter can override the defa 228 The --duration parameter can override the default run time of 30 minutes.
229 For example, ``--duration 2d`` would run for t 229 For example, ``--duration 2d`` would run for two days, ``--duration 3h``
230 would run for three hours, ``--duration 5m`` w 230 would run for three hours, ``--duration 5m`` would run for five minutes,
231 and ``--duration 45s`` would run for 45 second 231 and ``--duration 45s`` would run for 45 seconds. This last can be useful
232 for tracking down rare boot-time failures. 232 for tracking down rare boot-time failures.
233 233
234 Finally, the --trust-make parameter allows eac 234 Finally, the --trust-make parameter allows each kernel build to reuse what
235 it can from the previous kernel build. Please 235 it can from the previous kernel build. Please note that without the
236 --trust-make parameter, your tags files may be 236 --trust-make parameter, your tags files may be demolished.
237 237
238 There are additional more arcane arguments tha 238 There are additional more arcane arguments that are documented in the
239 source code of the kvm.sh script. 239 source code of the kvm.sh script.
240 240
241 If a run contains failures, the number of buil 241 If a run contains failures, the number of buildtime and runtime failures
242 is listed at the end of the kvm.sh output, whi 242 is listed at the end of the kvm.sh output, which you really should redirect
243 to a file. The build products and console out 243 to a file. The build products and console output of each run is kept in
244 tools/testing/selftests/rcutorture/res in time 244 tools/testing/selftests/rcutorture/res in timestamped directories. A
245 given directory can be supplied to kvm-find-er 245 given directory can be supplied to kvm-find-errors.sh in order to have
246 it cycle you through summaries of errors and f 246 it cycle you through summaries of errors and full error logs. For example::
247 247
248 tools/testing/selftests/rcutorture/bin 248 tools/testing/selftests/rcutorture/bin/kvm-find-errors.sh \
249 tools/testing/selftests/rcutor 249 tools/testing/selftests/rcutorture/res/2020.01.20-15.54.23
250 250
251 However, it is often more convenient to access 251 However, it is often more convenient to access the files directly.
252 Files pertaining to all scenarios in a run res 252 Files pertaining to all scenarios in a run reside in the top-level
253 directory (2020.01.20-15.54.23 in the example 253 directory (2020.01.20-15.54.23 in the example above), while per-scenario
254 files reside in a subdirectory named after the 254 files reside in a subdirectory named after the scenario (for example,
255 "TREE04"). If a given scenario ran more than 255 "TREE04"). If a given scenario ran more than once (as in "--configs
256 '56*TREE04'" above), the directories correspon 256 '56*TREE04'" above), the directories corresponding to the second and
257 subsequent runs of that scenario include a seq 257 subsequent runs of that scenario include a sequence number, for example,
258 "TREE04.2", "TREE04.3", and so on. 258 "TREE04.2", "TREE04.3", and so on.
259 259
260 The most frequently used file in the top-level 260 The most frequently used file in the top-level directory is testid.txt.
261 If the test ran in a git repository, then this 261 If the test ran in a git repository, then this file contains the commit
262 that was tested and any uncommitted changes in 262 that was tested and any uncommitted changes in diff format.
263 263
264 The most frequently used files in each per-sce 264 The most frequently used files in each per-scenario-run directory are:
265 265
266 .config: 266 .config:
267 This file contains the Kconfig options 267 This file contains the Kconfig options.
268 268
269 Make.out: 269 Make.out:
270 This contains build output for a speci 270 This contains build output for a specific scenario.
271 271
272 console.log: 272 console.log:
273 This contains the console output for a 273 This contains the console output for a specific scenario.
274 This file may be examined once the ker 274 This file may be examined once the kernel has booted, but
275 it might not exist if the build failed 275 it might not exist if the build failed.
276 276
277 vmlinux: 277 vmlinux:
278 This contains the kernel, which can be 278 This contains the kernel, which can be useful with tools like
279 objdump and gdb. 279 objdump and gdb.
280 280
281 A number of additional files are available, bu 281 A number of additional files are available, but are less frequently used.
282 Many are intended for debugging of rcutorture 282 Many are intended for debugging of rcutorture itself or of its scripting.
283 283
284 As of v5.4, a successful run with the default 284 As of v5.4, a successful run with the default set of scenarios produces
285 the following summary at the end of the run on 285 the following summary at the end of the run on a 12-CPU system::
286 286
287 SRCU-N ------- 804233 GPs (148.932/s) [src 287 SRCU-N ------- 804233 GPs (148.932/s) [srcu: g10008272 f0x0 ]
288 SRCU-P ------- 202320 GPs (37.4667/s) [src 288 SRCU-P ------- 202320 GPs (37.4667/s) [srcud: g1809476 f0x0 ]
289 SRCU-t ------- 1122086 GPs (207.794/s) [sr 289 SRCU-t ------- 1122086 GPs (207.794/s) [srcu: g0 f0x0 ]
290 SRCU-u ------- 1111285 GPs (205.794/s) [sr 290 SRCU-u ------- 1111285 GPs (205.794/s) [srcud: g1 f0x0 ]
291 TASKS01 ------- 19666 GPs (3.64185/s) [tas 291 TASKS01 ------- 19666 GPs (3.64185/s) [tasks: g0 f0x0 ]
292 TASKS02 ------- 20541 GPs (3.80389/s) [tas 292 TASKS02 ------- 20541 GPs (3.80389/s) [tasks: g0 f0x0 ]
293 TASKS03 ------- 19416 GPs (3.59556/s) [tas 293 TASKS03 ------- 19416 GPs (3.59556/s) [tasks: g0 f0x0 ]
294 TINY01 ------- 836134 GPs (154.84/s) [rcu: 294 TINY01 ------- 836134 GPs (154.84/s) [rcu: g0 f0x0 ] n_max_cbs: 34198
295 TINY02 ------- 850371 GPs (157.476/s) [rcu 295 TINY02 ------- 850371 GPs (157.476/s) [rcu: g0 f0x0 ] n_max_cbs: 2631
296 TREE01 ------- 162625 GPs (30.1157/s) [rcu 296 TREE01 ------- 162625 GPs (30.1157/s) [rcu: g1124169 f0x0 ]
297 TREE02 ------- 333003 GPs (61.6672/s) [rcu 297 TREE02 ------- 333003 GPs (61.6672/s) [rcu: g2647753 f0x0 ] n_max_cbs: 35844
298 TREE03 ------- 306623 GPs (56.782/s) [rcu: 298 TREE03 ------- 306623 GPs (56.782/s) [rcu: g2975325 f0x0 ] n_max_cbs: 1496497
299 CPU count limited from 16 to 12 299 CPU count limited from 16 to 12
300 TREE04 ------- 246149 GPs (45.5831/s) [rcu 300 TREE04 ------- 246149 GPs (45.5831/s) [rcu: g1695737 f0x0 ] n_max_cbs: 434961
301 TREE05 ------- 314603 GPs (58.2598/s) [rcu 301 TREE05 ------- 314603 GPs (58.2598/s) [rcu: g2257741 f0x2 ] n_max_cbs: 193997
302 TREE07 ------- 167347 GPs (30.9902/s) [rcu 302 TREE07 ------- 167347 GPs (30.9902/s) [rcu: g1079021 f0x0 ] n_max_cbs: 478732
303 CPU count limited from 16 to 12 303 CPU count limited from 16 to 12
304 TREE09 ------- 752238 GPs (139.303/s) [rcu 304 TREE09 ------- 752238 GPs (139.303/s) [rcu: g13075057 f0x0 ] n_max_cbs: 99011
305 305
306 306
307 Repeated Runs 307 Repeated Runs
308 ============= 308 =============
309 309
310 Suppose that you are chasing down a rare boot- 310 Suppose that you are chasing down a rare boot-time failure. Although you
311 could use kvm.sh, doing so will rebuild the ke 311 could use kvm.sh, doing so will rebuild the kernel on each run. If you
312 need (say) 1,000 runs to have confidence that 312 need (say) 1,000 runs to have confidence that you have fixed the bug,
313 these pointless rebuilds can become extremely 313 these pointless rebuilds can become extremely annoying.
314 314
315 This is why kvm-again.sh exists. 315 This is why kvm-again.sh exists.
316 316
317 Suppose that a previous kvm.sh run left its ou 317 Suppose that a previous kvm.sh run left its output in this directory::
318 318
319 tools/testing/selftests/rcutorture/res 319 tools/testing/selftests/rcutorture/res/2022.11.03-11.26.28
320 320
321 Then this run can be re-run without rebuilding 321 Then this run can be re-run without rebuilding as follow::
322 322
323 kvm-again.sh tools/testing/selftests/r 323 kvm-again.sh tools/testing/selftests/rcutorture/res/2022.11.03-11.26.28
324 324
325 A few of the original run's kvm.sh parameters 325 A few of the original run's kvm.sh parameters may be overridden, perhaps
326 most notably --duration and --bootargs. For e 326 most notably --duration and --bootargs. For example::
327 327
328 kvm-again.sh tools/testing/selftests/r 328 kvm-again.sh tools/testing/selftests/rcutorture/res/2022.11.03-11.26.28 \
329 --duration 45s 329 --duration 45s
330 330
331 would re-run the previous test, but for only 4 331 would re-run the previous test, but for only 45 seconds, thus facilitating
332 tracking down the aforementioned rare boot-tim 332 tracking down the aforementioned rare boot-time failure.
333 333
334 334
335 Distributed Runs 335 Distributed Runs
336 ================ 336 ================
337 337
338 Although kvm.sh is quite useful, its testing i 338 Although kvm.sh is quite useful, its testing is confined to a single
339 system. It is not all that hard to use your f 339 system. It is not all that hard to use your favorite framework to cause
340 (say) 5 instances of kvm.sh to run on your 5 s 340 (say) 5 instances of kvm.sh to run on your 5 systems, but this will very
341 likely unnecessarily rebuild kernels. In addi 341 likely unnecessarily rebuild kernels. In addition, manually distributing
342 the desired rcutorture scenarios across the av 342 the desired rcutorture scenarios across the available systems can be
343 painstaking and error-prone. 343 painstaking and error-prone.
344 344
345 And this is why the kvm-remote.sh script exist 345 And this is why the kvm-remote.sh script exists.
346 346
347 If you the following command works:: 347 If you the following command works::
348 348
349 ssh system0 date 349 ssh system0 date
350 350
351 and if it also works for system1, system2, sys 351 and if it also works for system1, system2, system3, system4, and system5,
352 and all of these systems have 64 CPUs, you can 352 and all of these systems have 64 CPUs, you can type::
353 353
354 kvm-remote.sh "system0 system1 system2 354 kvm-remote.sh "system0 system1 system2 system3 system4 system5" \
355 --cpus 64 --duration 8h --conf 355 --cpus 64 --duration 8h --configs "5*CFLIST"
356 356
357 This will build each default scenario's kernel 357 This will build each default scenario's kernel on the local system, then
358 spread each of five instances of each scenario 358 spread each of five instances of each scenario over the systems listed,
359 running each scenario for eight hours. At the 359 running each scenario for eight hours. At the end of the runs, the
360 results will be gathered, recorded, and printe 360 results will be gathered, recorded, and printed. Most of the parameters
361 that kvm.sh will accept can be passed to kvm-r 361 that kvm.sh will accept can be passed to kvm-remote.sh, but the list of
362 systems must come first. 362 systems must come first.
363 363
364 The kvm.sh ``--dryrun scenarios`` argument is 364 The kvm.sh ``--dryrun scenarios`` argument is useful for working out
365 how many scenarios may be run in one batch acr 365 how many scenarios may be run in one batch across a group of systems.
366 366
367 You can also re-run a previous remote run in a 367 You can also re-run a previous remote run in a manner similar to kvm.sh:
368 368
369 kvm-remote.sh "system0 system1 system2 369 kvm-remote.sh "system0 system1 system2 system3 system4 system5" \
370 tools/testing/selftests/rcutor 370 tools/testing/selftests/rcutorture/res/2022.11.03-11.26.28-remote \
371 --duration 24h 371 --duration 24h
372 372
373 In this case, most of the kvm-again.sh paramet 373 In this case, most of the kvm-again.sh parameters may be supplied following
374 the pathname of the old run-results directory. 374 the pathname of the old run-results directory.
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