treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157
[sfrench/cifs-2.6.git] / kernel / locking / qspinlock_stat.h
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 */