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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143/* SPDX-License-Identifier: GPL-2.0-or-later *//* * * Authors: Waiman Long <longman@redhat.com> */
#include "lock_events.h"
#ifdef CONFIG_LOCK_EVENT_COUNTS#ifdef CONFIG_PARAVIRT_SPINLOCKS/* * Collect pvqspinlock locking event counts */#include <linux/sched.h>#include <linux/sched/clock.h>#include <linux/fs.h>
#define EVENT_COUNT(ev) lockevents[LOCKEVENT_ ## ev]
/* * PV specific per-cpu counter */static DEFINE_PER_CPU(u64, pv_kick_time);
/* * Function to read and return the PV qspinlock counts. * * The following counters are handled specially: * 1. pv_latency_kick * Average kick latency (ns) = pv_latency_kick/pv_kick_unlock * 2. pv_latency_wake * Average wake latency (ns) = pv_latency_wake/pv_kick_wake * 3. pv_hash_hops * Average hops/hash = pv_hash_hops/pv_kick_unlock */ssize_t lockevent_read(struct file *file, char __user *user_buf, size_t count, loff_t *ppos){ char buf[64]; int cpu, id, len; u64 sum = 0, kicks = 0;
/* * Get the counter ID stored in file->f_inode->i_private */ id = (long)file_inode(file)->i_private;
if (id >= lockevent_num) return -EBADF;
for_each_possible_cpu(cpu) { sum += per_cpu(lockevents[id], cpu); /* * Need to sum additional counters for some of them */ switch (id) {
case LOCKEVENT_pv_latency_kick: case LOCKEVENT_pv_hash_hops: kicks += per_cpu(EVENT_COUNT(pv_kick_unlock), cpu); break;
case LOCKEVENT_pv_latency_wake: kicks += per_cpu(EVENT_COUNT(pv_kick_wake), cpu); break; } }
if (id == LOCKEVENT_pv_hash_hops) { u64 frac = 0;
if (kicks) { frac = 100ULL * do_div(sum, kicks); frac = DIV_ROUND_CLOSEST_ULL(frac, kicks); }
/* * Return a X.XX decimal number */ len = snprintf(buf, sizeof(buf) - 1, "%llu.%02llu\n", sum, frac); } else { /* * Round to the nearest ns */ if ((id == LOCKEVENT_pv_latency_kick) || (id == LOCKEVENT_pv_latency_wake)) { if (kicks) sum = DIV_ROUND_CLOSEST_ULL(sum, kicks); } len = snprintf(buf, sizeof(buf) - 1, "%llu\n", sum); }
return simple_read_from_buffer(user_buf, count, ppos, buf, len);}
/* * PV hash hop count */static inline void lockevent_pv_hop(int hopcnt){ this_cpu_add(EVENT_COUNT(pv_hash_hops), hopcnt);}
/* * Replacement function for pv_kick() */static inline void __pv_kick(int cpu){ u64 start = sched_clock();
per_cpu(pv_kick_time, cpu) = start; pv_kick(cpu); this_cpu_add(EVENT_COUNT(pv_latency_kick), sched_clock() - start);}
/* * Replacement function for pv_wait() */static inline void __pv_wait(u8 *ptr, u8 val){ u64 *pkick_time = this_cpu_ptr(&pv_kick_time);
*pkick_time = 0; pv_wait(ptr, val); if (*pkick_time) { this_cpu_add(EVENT_COUNT(pv_latency_wake), sched_clock() - *pkick_time); lockevent_inc(pv_kick_wake); }}
#define pv_kick(c) __pv_kick(c)#define pv_wait(p, v) __pv_wait(p, v)
#endif /* CONFIG_PARAVIRT_SPINLOCKS */
#else /* CONFIG_LOCK_EVENT_COUNTS */
static inline void lockevent_pv_hop(int hopcnt) { }
#endif /* CONFIG_LOCK_EVENT_COUNTS */