timer_stats.c 9.98 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425
/*
 * 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_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);
}

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;

	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;
}

/**
 * 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 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.timer_flag = timer_flag;

	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);
}

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: v0.3\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->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) {
		raw_spinlock_t *lock = &per_cpu(tstats_lookup_lock, cpu);

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

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);