1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 *
4 * Authors: Waiman Long <longman@redhat.com>
5 */
6
7 #include "lock_events.h"
8
9 #ifdef CONFIG_LOCK_EVENT_COUNTS
10 #ifdef CONFIG_PARAVIRT_SPINLOCKS
11 /*
12 * Collect pvqspinlock locking event counts
13 */
14 #include <linux/sched.h>
15 #include <linux/sched/clock.h>
16 #include <linux/fs.h>
17
18 #define EVENT_COUNT(ev) lockevents[LOCKEVENT_ ## ev]
19
20 /*
21 * PV specific per-cpu counter
22 */
23 static DEFINE_PER_CPU(u64, pv_kick_time);
24
25 /*
26 * Function to read and return the PV qspinlock counts.
27 *
28 * The following counters are handled specially:
29 * 1. pv_latency_kick
30 * Average kick latency (ns) = pv_latency_kick/pv_kick_unlock
31 * 2. pv_latency_wake
32 * Average wake latency (ns) = pv_latency_wake/pv_kick_wake
33 * 3. pv_hash_hops
34 * Average hops/hash = pv_hash_hops/pv_kick_unlock
35 */
36 ssize_t lockevent_read(struct file *file, char __user *user_buf,
37 size_t count, loff_t *ppos)
38 {
39 char buf[64];
40 int cpu, id, len;
41 u64 sum = 0, kicks = 0;
42
43 /*
44 * Get the counter ID stored in file->f_inode->i_private
45 */
46 id = (long)file_inode(file)->i_private;
47
48 if (id >= lockevent_num)
49 return -EBADF;
50
51 for_each_possible_cpu(cpu) {
52 sum += per_cpu(lockevents[id], cpu);
53 /*
54 * Need to sum additional counters for some of them
55 */
56 switch (id) {
57
58 case LOCKEVENT_pv_latency_kick:
59 case LOCKEVENT_pv_hash_hops:
60 kicks += per_cpu(EVENT_COUNT(pv_kick_unlock), cpu);
61 break;
62
63 case LOCKEVENT_pv_latency_wake:
64 kicks += per_cpu(EVENT_COUNT(pv_kick_wake), cpu);
65 break;
66 }
67 }
68
69 if (id == LOCKEVENT_pv_hash_hops) {
70 u64 frac = 0;
71
72 if (kicks) {
73 frac = 100ULL * do_div(sum, kicks);
74 frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
75 }
76
77 /*
78 * Return a X.XX decimal number
79 */
80 len = snprintf(buf, sizeof(buf) - 1, "%llu.%02llu\n",
81 sum, frac);
82 } else {
83 /*
84 * Round to the nearest ns
85 */
86 if ((id == LOCKEVENT_pv_latency_kick) ||
87 (id == LOCKEVENT_pv_latency_wake)) {
88 if (kicks)
89 sum = DIV_ROUND_CLOSEST_ULL(sum, kicks);
90 }
91 len = snprintf(buf, sizeof(buf) - 1, "%llu\n", sum);
92 }
93
94 return simple_read_from_buffer(user_buf, count, ppos, buf, len);
95 }
96
97 /*
98 * PV hash hop count
99 */
100 static inline void lockevent_pv_hop(int hopcnt)
101 {
102 this_cpu_add(EVENT_COUNT(pv_hash_hops), hopcnt);
103 }
104
105 /*
106 * Replacement function for pv_kick()
107 */
108 static inline void __pv_kick(int cpu)
109 {
110 u64 start = sched_clock();
111
112 per_cpu(pv_kick_time, cpu) = start;
113 pv_kick(cpu);
114 this_cpu_add(EVENT_COUNT(pv_latency_kick), sched_clock() - start);
115 }
116
117 /*
118 * Replacement function for pv_wait()
119 */
120 static inline void __pv_wait(u8 *ptr, u8 val)
121 {
122 u64 *pkick_time = this_cpu_ptr(&pv_kick_time);
123
124 *pkick_time = 0;
125 pv_wait(ptr, val);
126 if (*pkick_time) {
127 this_cpu_add(EVENT_COUNT(pv_latency_wake),
128 sched_clock() - *pkick_time);
129 lockevent_inc(pv_kick_wake);
130 }
131 }
132
133 #define pv_kick(c) __pv_kick(c)
134 #define pv_wait(p, v) __pv_wait(p, v)
135
136 #endif /* CONFIG_PARAVIRT_SPINLOCKS */
137
138 #else /* CONFIG_LOCK_EVENT_COUNTS */
139
140 static inline void lockevent_pv_hop(int hopcnt) { }
141
142 #endif /* CONFIG_LOCK_EVENT_COUNTS */
143
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