Release 4.7 kernel/time/timer_stats.c

/*
 * 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;
	
u32			flags;

	/*
         * 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_RAW_SPINLOCK(table_lock);

/*
 * Per-CPU lookup locks for fast hash lookup:
 */
static DEFINE_PER_CPU(raw_spinlock_t, tstats_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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
32
72.73%
1
50.00%
bjorn steinbrink
bjorn steinbrink
12
27.27%
1
50.00%
Total
44
100.00%
2
100.00%



static struct entry *alloc_entry(void)
{
	if (nr_entries >= MAX_ENTRIES)
		return NULL;

	return entries + nr_entries++;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
25
100.00%
1
100.00%
Total
25
100.00%
1
100.00%



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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
49
100.00%
1
100.00%
Total
49
100.00%
1
100.00%

/*
 * 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;

	raw_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:
	raw_spin_unlock(&table_lock);

	return curr;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
170
93.41%
1
33.33%
bjorn steinbrink
bjorn steinbrink
10
5.49%
1
33.33%
thomas gleixner
thomas gleixner
2
1.10%
1
33.33%
Total
182
100.00%
3
100.00%

/**
 * 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
 * @tflags:     The flags field of 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, u32 tflags)
{
	/*
         * It doesn't matter which lock we take:
         */
	raw_spinlock_t *lock;
	struct entry *entry, input;
	unsigned long flags;

	if (likely(!timer_stats_active))
		return;

	lock = &per_cpu(tstats_lookup_lock, raw_smp_processor_id());

	input.timer = timer;
	input.start_func = startf;
	input.expire_func = timerf;
	input.pid = pid;
	input.flags = tflags;

	raw_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:
	raw_spin_unlock_irqrestore(lock, flags);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
130
89.04%
2
25.00%
thomas gleixner
thomas gleixner
7
4.79%
2
25.00%
venkatesh pallipadi
venkatesh pallipadi
5
3.42%
1
12.50%
heiko carstens
heiko carstens
2
1.37%
1
12.50%
tejun heo
tejun heo
1
0.68%
1
12.50%
lucas de marchi
lucas de marchi
1
0.68%
1
12.50%
Total
146
100.00%
8
100.00%



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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
40
72.73%
1
50.00%
alexey dobriyan
alexey dobriyan
15
27.27%
1
50.00%
Total
55
100.00%
2
100.00%



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: v0.3\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));
	seq_printf(m, "Collection: %s\n", timer_stats_active ? "active" : "inactive");

	for (i = 0; i < nr_entries; i++) {
		entry = entries + i;
		if (entry->flags & TIMER_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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
263
82.19%
1
16.67%
venkatesh pallipadi
venkatesh pallipadi
31
9.69%
1
16.67%
dong zhu
dong zhu
14
4.38%
1
16.67%
anton blanchard
anton blanchard
9
2.81%
1
16.67%
thomas gleixner
thomas gleixner
2
0.62%
1
16.67%
heiko carstens
heiko carstens
1
0.31%
1
16.67%
Total
320
100.00%
6
100.00%

/*
 * 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) {
		raw_spinlock_t *lock = &per_cpu(tstats_lookup_lock, cpu);

		raw_spin_lock_irqsave(lock, flags);
		/* nothing */
		raw_spin_unlock_irqrestore(lock, flags);
	}
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
37
77.08%
1
33.33%
tejun heo
tejun heo
8
16.67%
1
33.33%
thomas gleixner
thomas gleixner
3
6.25%
1
33.33%
Total
48
100.00%
3
100.00%



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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
129
94.85%
1
33.33%
heiko carstens
heiko carstens
4
2.94%
1
33.33%
bjorn steinbrink
bjorn steinbrink
3
2.21%
1
33.33%
Total
136
100.00%
3
100.00%



static int tstats_open(struct inode *inode, struct file *filp)
{
	return single_open(filp, tstats_show, NULL);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
26
100.00%
1
100.00%
Total
26
100.00%
1
100.00%


static const 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)
		raw_spin_lock_init(&per_cpu(tstats_lookup_lock, cpu));
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
24
92.31%
1
33.33%
tejun heo
tejun heo
1
3.85%
1
33.33%
thomas gleixner
thomas gleixner
1
3.85%
1
33.33%
Total
26
100.00%
3
100.00%



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;
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
36
90.00%
1
50.00%
denis v. lunev
denis v. lunev
4
10.00%
1
50.00%
Total
40
100.00%
2
100.00%


__initcall(init_tstats_procfs);
Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
ingo molnar
ingo molnar
1120
85.82%
2
11.76%
bjorn steinbrink
bjorn steinbrink
63
4.83%
1
5.88%
venkatesh pallipadi
venkatesh pallipadi
37
2.84%
1
5.88%
thomas gleixner
thomas gleixner
20
1.53%
3
17.65%
alexey dobriyan
alexey dobriyan
17
1.30%
3
17.65%
dong zhu
dong zhu
14
1.07%
1
5.88%
tejun heo
tejun heo
11
0.84%
1
5.88%
anton blanchard
anton blanchard
9
0.69%
1
5.88%
heiko carstens
heiko carstens
8
0.61%
1
5.88%
denis v. lunev
denis v. lunev
4
0.31%
1
5.88%
lucas de marchi
lucas de marchi
1
0.08%
1
5.88%
pavel machek
pavel machek
1
0.08%
1
5.88%
Total
1305
100.00%
17
100.00%
  
Directory: kernel/time

Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.