/* * 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(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; 	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 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: v0.2\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) {		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);