/*
* kernel/time/timer_stats.c
*
* Collect timer usage statistics.
*
* Copyright(C) 2006, Red Hat, Inc., Ingo Molnar
* Copyright(C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
*
* timer_stats is based on timer_top, a similar functionality which was part of
* Con Kolivas dyntick patch set. It was developed by Daniel Petrini at the
* Instituto Nokia de Tecnologia - INdT - Manaus. timer_top's design was based
* on dynamic allocation of the statistics entries and linear search based
* lookup combined with a global lock, rather than the static array, hash
* and per-CPU locking which is used by timer_stats. It was written for the
* pre hrtimer kernel code and therefore did not take hrtimers into account.
* Nevertheless it provided the base for the timer_stats implementation and
* was a helpful source of inspiration. Kudos to Daniel and the Nokia folks
* for this effort.
*
* timer_top.c is
* Copyright (C) 2005 Instituto Nokia de Tecnologia - INdT - Manaus
* Written by Daniel Petrini <d.pensator@gmail.com>
* timer_top.c was released under the GNU General Public License version 2
*
* We export the addresses and counting of timer functions being called,
* the pid and cmdline from the owner process if applicable.
*
* Start/stop data collection:
* # echo [1|0] >/proc/timer_stats
*
* Display the information collected so far:
* # cat /proc/timer_stats
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/proc_fs.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/kallsyms.h>
#include <asm/uaccess.h>
/*
* This is our basic unit of interest: a timer expiry event identified
* by the timer, its start/expire functions and the PID of the task that
* started the timer. We count the number of times an event happens:
*/
struct entry {
/*
* Hash list:
*/
struct entry *next;
/*
* Hash keys:
*/
void *timer;
void *start_func;
void *expire_func;
pid_t pid;
/*
* Number of timeout events:
*/
unsigned long count;
unsigned int timer_flag;
/*
* We save the command-line string to preserve
* this information past task exit:
*/
char comm[TASK_COMM_LEN + 1];
} ____cacheline_aligned_in_smp;
/*
* Spinlock protecting the tables - not taken during lookup:
*/
static DEFINE_SPINLOCK(table_lock);
/*
* Per-CPU lookup locks for fast hash lookup:
*/
static DEFINE_PER_CPU(spinlock_t, lookup_lock);
/*
* Mutex to serialize state changes with show-stats activities:
*/
static DEFINE_MUTEX(show_mutex);
/*
* Collection status, active/inactive:
*/
int __read_mostly timer_stats_active;
/*
* Beginning/end timestamps of measurement:
*/
static ktime_t time_start, time_stop;
/*
* tstat entry structs only get allocated while collection is
* active and never freed during that time - this simplifies
* things quite a bit.
*
* They get freed when a new collection period is started.
*/
#define MAX_ENTRIES_BITS 10
#define MAX_ENTRIES (1UL << MAX_ENTRIES_BITS)
static unsigned long nr_entries;
static struct entry entries[MAX_ENTRIES];
static atomic_t overflow_count;
/*
* The entries are in a hash-table, for fast lookup:
*/
#define TSTAT_HASH_BITS (MAX_ENTRIES_BITS - 1)
#define TSTAT_HASH_SIZE (1UL << TSTAT_HASH_BITS)
#define TSTAT_HASH_MASK (TSTAT_HASH_SIZE - 1)
#define __tstat_hashfn(entry) \
(((unsigned long)(entry)->timer ^ \
(unsigned long)(entry)->start_func ^ \
(unsigned long)(entry)->expire_func ^ \
(unsigned long)(entry)->pid ) & TSTAT_HASH_MASK)
#define tstat_hashentry(entry) (tstat_hash_table + __tstat_hashfn(entry))
static struct entry *tstat_hash_table[TSTAT_HASH_SIZE] __read_mostly;
static void reset_entries(void)
{
nr_entries = 0;
memset(entries, 0, sizeof(entries));
memset(tstat_hash_table, 0, sizeof(tstat_hash_table));
atomic_set(&overflow_count, 0);
}
static struct entry *alloc_entry(void)
{
if (nr_entries >= MAX_ENTRIES)
return NULL;
return entries + nr_entries++;
}
static int match_entries(struct entry *entry1, struct entry *entry2)
{
return entry1->timer == entry2->timer &&
entry1->start_func == entry2->start_func &&
entry1->expire_func == entry2->expire_func &&
entry1->pid == entry2->pid;
}
/*
* Look up whether an entry matching this item is present
* in the hash already. Must be called with irqs off and the
* lookup lock held:
*/
static struct entry *tstat_lookup(struct entry *entry, char *comm)
{
struct entry **head, *curr, *prev;
head = tstat_hashentry(entry);
curr = *head;
/*
* The fastpath is when the entry is already hashed,
* we do this with the lookup lock held, but with the
* table lock not held:
*/
while (curr) {
if (match_entries(curr, entry))
return curr;
curr = curr->next;
}
/*
* Slowpath: allocate, set up and link a new hash entry:
*/
prev = NULL;
curr = *head;
spin_lock(&table_lock);
/*
* Make sure we have not raced with another CPU:
*/
while (curr) {
if (match_entries(curr, entry))
goto out_unlock;
prev = curr;
curr = curr->next;
}
curr = alloc_entry();
if (curr) {
*curr = *entry;
curr->count = 0;
curr->next = NULL;
memcpy(curr->comm, comm, TASK_COMM_LEN);
smp_mb(); /* Ensure that curr is initialized before insert */
if (prev)
prev->next = curr;
else
*head = curr;
}
out_unlock:
spin_unlock(&table_lock);
return curr;
}
/**
* timer_stats_update_stats - Update the statistics for a timer.
* @timer: pointer to either a timer_list or a hrtimer
* @pid: the pid of the task which set up the timer
* @startf: pointer to the function which did the timer setup
* @timerf: pointer to the timer callback function of the timer
* @comm: name of the process which set up the timer
*
* When the timer is already registered, then the event counter is
* incremented. Otherwise the timer is registered in a free slot.
*/
void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
void *timerf, char *comm,
unsigned int timer_flag)
{
/*
* It doesnt matter which lock we take:
*/
spinlock_t *lock;
struct entry *entry, input;
unsigned long flags;
if (likely(!timer_stats_active))
return;
lock = &per_cpu(lookup_lock, raw_smp_processor_id());
input.timer = timer;
input.start_func = startf;
input.expire_func = timerf;
input.pid = pid;
input.timer_flag = timer_flag;
spin_lock_irqsave(lock, flags);
if (!timer_stats_active)
goto out_unlock;
entry = tstat_lookup(&input, comm);
if (likely(entry))
entry->count++;
else
atomic_inc(&overflow_count);
out_unlock:
spin_unlock_irqrestore(lock, flags);
}
static void print_name_offset(struct seq_file *m, unsigned long addr)
{
char symname[KSYM_NAME_LEN];
if (lookup_symbol_name(addr, symname) < 0)
seq_printf(m, "<%p>", (void *)addr);
else
seq_printf(m, "%s", symname);
}
static int tstats_show(struct seq_file *m, void *v)
{
struct timespec period;
struct entry *entry;
unsigned long ms;
long events = 0;
ktime_t time;
int i;
mutex_lock(&show_mutex);
/*
* If still active then calculate up to now:
*/
if (timer_stats_active)
time_stop = ktime_get();
time = ktime_sub(time_stop, time_start);
period = ktime_to_timespec(time);
ms = period.tv_nsec / 1000000;
seq_puts(m, "Timer Stats Version: v0.2\n");
seq_printf(m, "Sample period: %ld.%03ld s\n", period.tv_sec, ms);
if (atomic_read(&overflow_count))
seq_printf(m, "Overflow: %d entries\n",
atomic_read(&overflow_count));
for (i = 0; i < nr_entries; i++) {
entry = entries + i;
if (entry->timer_flag & TIMER_STATS_FLAG_DEFERRABLE) {
seq_printf(m, "%4luD, %5d %-16s ",
entry->count, entry->pid, entry->comm);
} else {
seq_printf(m, " %4lu, %5d %-16s ",
entry->count, entry->pid, entry->comm);
}
print_name_offset(m, (unsigned long)entry->start_func);
seq_puts(m, " (");
print_name_offset(m, (unsigned long)entry->expire_func);
seq_puts(m, ")\n");
events += entry->count;
}
ms += period.tv_sec * 1000;
if (!ms)
ms = 1;
if (events && period.tv_sec)
seq_printf(m, "%ld total events, %ld.%03ld events/sec\n",
events, events * 1000 / ms,
(events * 1000000 / ms) % 1000);
else
seq_printf(m, "%ld total events\n", events);
mutex_unlock(&show_mutex);
return 0;
}
/*
* After a state change, make sure all concurrent lookup/update
* activities have stopped:
*/
static void sync_access(void)
{
unsigned long flags;
int cpu;
for_each_online_cpu(cpu) {
spin_lock_irqsave(&per_cpu(lookup_lock, cpu), flags);
/* nothing */
spin_unlock_irqrestore(&per_cpu(lookup_lock, cpu), flags);
}
}
static ssize_t tstats_write(struct file *file, const char __user *buf,
size_t count, loff_t *offs)
{
char ctl[2];
if (count != 2 || *offs)
return -EINVAL;
if (copy_from_user(ctl, buf, count))
return -EFAULT;
mutex_lock(&show_mutex);
switch (ctl[0]) {
case '0':
if (timer_stats_active) {
timer_stats_active = 0;
time_stop = ktime_get();
sync_access();
}
break;
case '1':
if (!timer_stats_active) {
reset_entries();
time_start = ktime_get();
smp_mb();
timer_stats_active = 1;
}
break;
default:
count = -EINVAL;
}
mutex_unlock(&show_mutex);
return count;
}
static int tstats_open(struct inode *inode, struct file *filp)
{
return single_open(filp, tstats_show, NULL);
}
static struct file_operations tstats_fops = {
.open = tstats_open,
.read = seq_read,
.write = tstats_write,
.llseek = seq_lseek,
.release = single_release,
};
void __init init_timer_stats(void)
{
int cpu;
for_each_possible_cpu(cpu)
spin_lock_init(&per_cpu(lookup_lock, cpu));
}
static int __init init_tstats_procfs(void)
{
struct proc_dir_entry *pe;
pe = proc_create("timer_stats", 0644, NULL, &tstats_fops);
if (!pe)
return -ENOMEM;
return 0;
}
__initcall(init_tstats_procfs);
