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/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* 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 */
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