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    Subject[patch 21/21] debugging feature: timer stats
    From: Thomas Gleixner <tglx@linutronix.de>

    add /proc/timer_stats support: debugging feature to profile timer expiration.
    Both the starting site, process/PID and the expiration function is
    captured. This allows the quick identification of timer event sources
    in a system.

    sample output:

    # echo 1 > /proc/tstats
    # cat /proc/tstats
    Timerstats sample period: 3.888770 s
    12, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
    15, 1 swapper hcd_submit_urb (rh_timer_func)
    4, 959 kedac schedule_timeout (process_timeout)
    1, 0 swapper page_writeback_init (wb_timer_fn)
    28, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
    22, 2948 IRQ 4 tty_flip_buffer_push (delayed_work_timer_fn)
    3, 3100 bash schedule_timeout (process_timeout)
    1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
    1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
    1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
    1, 2292 ip __netdev_watchdog_up (dev_watchdog)
    1, 23 events/1 do_cache_clean (delayed_work_timer_fn)
    90 total events, 30.0 events/sec
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    --
    Documentation/hrtimer/timer_stats.txt | 68 +++++++++
    include/linux/hrtimer.h | 53 +++++++
    include/linux/timer.h | 49 ++++++
    kernel/hrtimer.c | 28 +++
    kernel/time/Makefile | 3
    kernel/time/timer_stats.c | 244 ++++++++++++++++++++++++++++++++++
    kernel/timer.c | 29 +++-
    kernel/workqueue.c | 6
    lib/Kconfig.debug | 11 +
    9 files changed, 484 insertions(+), 7 deletions(-)
    Index: linux-2.6.18-mm2/include/linux/hrtimer.h
    ===================================================================
    --- linux-2.6.18-mm2.orig/include/linux/hrtimer.h 2006-10-02 00:55:54.000000000 +0200
    +++ linux-2.6.18-mm2/include/linux/hrtimer.h 2006-10-02 00:55:55.000000000 +0200
    @@ -101,8 +101,14 @@ enum hrtimer_cb_mode {
    * @cb_mode: high resolution timer feature to select the callback execution
    * mode
    * @cb_entry: list head to enqueue an expired timer into the callback list
    + * @start_site: timer statistics field to store the site where the timer
    + * was started
    + * @start_comm: timer statistics field to store the name of the process which
    + * started the timer
    + * @start_pid: timer statistics field to store the pid of the task which
    + * started the timer
    *
    - * The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
    + * The hrtimer structure must be initialized by hrtimer_init()
    */
    struct hrtimer {
    struct rb_node node;
    @@ -114,6 +120,11 @@ struct hrtimer {
    enum hrtimer_cb_mode cb_mode;
    struct list_head cb_entry;
    #endif
    +#ifdef CONFIG_TIMER_STATS
    + void *start_site;
    + char start_comm[16];
    + int start_pid;
    +#endif
    };

    /**
    @@ -333,4 +344,44 @@ static inline void show_no_hz_stats(stru
    /* Bootup initialization: */
    extern void __init hrtimers_init(void);

    +/*
    + * Timer-statistics info:
    + */
    +#ifdef CONFIG_TIMER_STATS
    +
    +extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
    + void *timerf, char * comm);
    +
    +static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
    +{
    + timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
    + timer->function, timer->start_comm);
    +}
    +
    +extern void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer,
    + void *addr);
    +
    +static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
    +{
    + __timer_stats_hrtimer_set_start_info(timer, __builtin_return_address(0));
    +}
    +
    +static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
    +{
    + timer->start_site = NULL;
    +}
    +#else
    +static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
    +{
    +}
    +
    +static inline void timer_tstats_hrtimer_set_start_info(struct hrtimer *timer)
    +{
    +}
    +
    +static inline void timer_tstats_hrtimer_clear_start_info(struct hrtimer *timer)
    +{
    +}
    +#endif
    +
    #endif
    Index: linux-2.6.18-mm2/include/linux/timer.h
    ===================================================================
    --- linux-2.6.18-mm2.orig/include/linux/timer.h 2006-10-02 00:55:52.000000000 +0200
    +++ linux-2.6.18-mm2/include/linux/timer.h 2006-10-02 00:55:55.000000000 +0200
    @@ -2,6 +2,7 @@
    #define _LINUX_TIMER_H

    #include <linux/list.h>
    +#include <linux/ktime.h>
    #include <linux/spinlock.h>
    #include <linux/stddef.h>

    @@ -15,6 +16,11 @@ struct timer_list {
    unsigned long data;

    struct tvec_t_base_s *base;
    +#ifdef CONFIG_TIMER_STATS
    + void *start_site;
    + char start_comm[16];
    + int start_pid;
    +#endif
    };

    extern struct tvec_t_base_s boot_tvec_bases;
    @@ -73,6 +79,49 @@ extern unsigned long next_timer_interrup
    */
    extern unsigned long get_next_timer_interrupt(unsigned long now);

    +/*
    + * Timer-statistics info:
    + */
    +#ifdef CONFIG_TIMER_STATS
    +
    +extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
    + void *timerf, char * comm);
    +
    +static inline void timer_stats_account_timer(struct timer_list *timer)
    +{
    + timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
    + timer->function, timer->start_comm);
    +}
    +
    +extern void __timer_stats_timer_set_start_info(struct timer_list *timer,
    + void *addr);
    +
    +static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
    +{
    + __timer_stats_timer_set_start_info(timer, __builtin_return_address(0));
    +}
    +
    +static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
    +{
    + timer->start_site = NULL;
    +}
    +#else
    +static inline void timer_stats_account_timer(struct timer_list *timer)
    +{
    +}
    +
    +static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
    +{
    +}
    +
    +static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
    +{
    +}
    +#endif
    +
    +extern void delayed_work_timer_fn(unsigned long __data);
    +
    +
    /***
    * add_timer - start a timer
    * @timer: the timer to be added
    Index: linux-2.6.18-mm2/kernel/hrtimer.c
    ===================================================================
    --- linux-2.6.18-mm2.orig/kernel/hrtimer.c 2006-10-02 00:55:54.000000000 +0200
    +++ linux-2.6.18-mm2/kernel/hrtimer.c 2006-10-02 00:55:55.000000000 +0200
    @@ -457,7 +457,7 @@ static void update_jiffies64(ktime_t now
    delta = ktime_sub(now, last_jiffies_update);
    } while (read_seqretry(&xtime_lock, seq));

    - if (delta.tv64 >= nsec_per_hz.tv64)
    + if (delta.tv64 < nsec_per_hz.tv64)
    return;

    /* Reevalute with xtime_lock held */
    @@ -909,6 +909,18 @@ static inline void hrtimer_resume_jiffy_

    #endif /* CONFIG_HIGH_RES_TIMERS */

    +#ifdef CONFIG_TIMER_STATS
    +void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer, void *addr)
    +{
    + if (timer->start_site)
    + return;
    +
    + timer->start_site = addr;
    + memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
    + timer->start_pid = current->pid;
    +}
    +#endif
    +
    /*
    * Timekeeping resumed notification
    */
    @@ -1077,6 +1089,7 @@ remove_hrtimer(struct hrtimer *timer, st
    * reprogramming happens in the interrupt handler. This is a
    * rare case and less expensive than a smp call.
    */
    + timer_stats_hrtimer_clear_start_info(timer);
    reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
    __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE,
    reprogram);
    @@ -1125,6 +1138,8 @@ hrtimer_start(struct hrtimer *timer, kti
    }
    timer->expires = tim;

    + timer_stats_hrtimer_set_start_info(timer);
    +
    enqueue_hrtimer(timer, new_base, base == new_base);

    unlock_hrtimer_base(timer, &flags);
    @@ -1257,6 +1272,12 @@ void hrtimer_init(struct hrtimer *timer,

    timer->base = &cpu_base->clock_base[clock_id];
    hrtimer_init_timer_hres(timer);
    +
    +#ifdef CONFIG_TIMER_STATS
    + timer->start_site = NULL;
    + timer->start_pid = -1;
    + memset(timer->start_comm, 0, TASK_COMM_LEN);
    +#endif
    }
    EXPORT_SYMBOL_GPL(hrtimer_init);

    @@ -1343,6 +1364,7 @@ void hrtimer_interrupt(struct pt_regs *r

    __remove_hrtimer(timer, base,
    HRTIMER_STATE_CALLBACK, 0);
    + timer_stats_account_hrtimer(timer);

    if (timer->function(timer) != HRTIMER_NORESTART) {
    BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
    @@ -1388,6 +1410,8 @@ static void run_hrtimer_softirq(struct s
    timer = list_entry(cpu_base->cb_pending.next,
    struct hrtimer, cb_entry);

    + timer_stats_account_hrtimer(timer);
    +
    fn = timer->function;
    __remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
    spin_unlock_irq(&cpu_base->lock);
    @@ -1444,6 +1468,8 @@ static inline void run_hrtimer_queue(str
    if (base->softirq_time.tv64 <= timer->expires.tv64)
    break;

    + timer_stats_account_hrtimer(timer);
    +
    fn = timer->function;
    __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
    spin_unlock_irq(&cpu_base->lock);
    Index: linux-2.6.18-mm2/kernel/time/Makefile
    ===================================================================
    --- linux-2.6.18-mm2.orig/kernel/time/Makefile 2006-10-02 00:55:53.000000000 +0200
    +++ linux-2.6.18-mm2/kernel/time/Makefile 2006-10-02 00:55:55.000000000 +0200
    @@ -1,3 +1,4 @@
    obj-y += ntp.o clocksource.o jiffies.o

    -obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
    +obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
    +obj-$(CONFIG_TIMER_STATS) += timer_stats.o
    Index: linux-2.6.18-mm2/kernel/time/timer_stats.c
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-2.6.18-mm2/kernel/time/timer_stats.c 2006-10-02 00:55:55.000000000 +0200
    @@ -0,0 +1,244 @@
    +/*
    + * 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 rather than the static array
    + * which is used by timer_stats. It was written for the pre hrtimer kernel code
    + * and therefor did not take hrtimers into account. Nevertheless it provided
    + * the base for the timer_stats implementation and was a helpful source of
    + * inspiration in the first place. 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 collected information:
    + * # 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/list.h>
    +#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>
    +
    +enum tstats_stat {
    + TSTATS_INACTIVE,
    + TSTATS_ACTIVE,
    + TSTATS_READOUT,
    + TSTATS_RESET,
    +};
    +
    +struct tstats_entry {
    + void *timer;
    + void *start_func;
    + void *expire_func;
    + unsigned long counter;
    + pid_t pid;
    + char comm[TASK_COMM_LEN + 1];
    +};
    +
    +#define TSTATS_MAX_ENTRIES 1024
    +
    +static struct tstats_entry tstats[TSTATS_MAX_ENTRIES];
    +static DEFINE_SPINLOCK(tstats_lock);
    +static enum tstats_stat tstats_status;
    +static ktime_t tstats_time;
    +
    +/**
    + * 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)
    +{
    + struct tstats_entry *entry = tstats;
    + unsigned long flags;
    + int i;
    +
    + spin_lock_irqsave(&tstats_lock, flags);
    + if (tstats_status != TSTATS_ACTIVE)
    + goto out_unlock;
    +
    + for (i = 0; i < TSTATS_MAX_ENTRIES; i++, entry++) {
    + if (entry->timer == timer &&
    + entry->start_func == startf &&
    + entry->expire_func == timerf &&
    + entry->pid == pid) {
    +
    + entry->counter++;
    + break;
    + }
    + if (!entry->timer) {
    + entry->timer = timer;
    + entry->start_func = startf;
    + entry->expire_func = timerf;
    + entry->counter = 1;
    + entry->pid = pid;
    + memcpy(entry->comm, comm, TASK_COMM_LEN);
    + entry->comm[TASK_COMM_LEN] = 0;
    + break;
    + }
    + }
    +
    + out_unlock:
    + spin_unlock_irqrestore(&tstats_lock, flags);
    +}
    +
    +static void print_name_offset(struct seq_file *m, unsigned long addr)
    +{
    + char namebuf[KSYM_NAME_LEN+1];
    + unsigned long size, offset;
    + const char *sym_name;
    + char *modname;
    +
    + sym_name = kallsyms_lookup(addr, &size, &offset, &modname, namebuf);
    + if (sym_name)
    + seq_printf(m, "%s", sym_name);
    + else
    + seq_printf(m, "<%p>", (void *)addr);
    +}
    +
    +static int tstats_show(struct seq_file *m, void *v)
    +{
    + struct tstats_entry *entry = tstats;
    + struct timespec period;
    + unsigned long ms;
    + long events = 0;
    + int i;
    +
    + spin_lock_irq(&tstats_lock);
    + switch(tstats_status) {
    + case TSTATS_ACTIVE:
    + tstats_time = ktime_sub(ktime_get(), tstats_time);
    + case TSTATS_INACTIVE:
    + tstats_status = TSTATS_READOUT;
    + break;
    + default:
    + spin_unlock_irq(&tstats_lock);
    + return -EBUSY;
    + }
    + spin_unlock_irq(&tstats_lock);
    +
    + period = ktime_to_timespec(tstats_time);
    + ms = period.tv_nsec % 1000000;
    +
    + seq_printf(m, "Timerstats sample period: %ld.%3ld s\n",
    + period.tv_sec, ms);
    +
    + for (i = 0; i < TSTATS_MAX_ENTRIES && entry->timer; i++, entry++) {
    + seq_printf(m, "%4lu, %5d %-16s ", entry->counter, 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->counter;
    + }
    +
    + ms += period.tv_sec * 1000;
    + if (events && period.tv_sec)
    + seq_printf(m, "%ld total events, %ld.%ld events/sec\n", events,
    + events / period.tv_sec, events * 1000 / ms);
    + else
    + seq_printf(m, "%ld total events\n", events);
    +
    + tstats_status = TSTATS_INACTIVE;
    + return 0;
    +}
    +
    +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;
    +
    + switch (ctl[0]) {
    + case '0':
    + spin_lock_irq(&tstats_lock);
    + if (tstats_status == TSTATS_ACTIVE) {
    + tstats_status = TSTATS_INACTIVE;
    + tstats_time = ktime_sub(ktime_get(), tstats_time);
    + }
    + spin_unlock_irq(&tstats_lock);
    + break;
    + case '1':
    + spin_lock_irq(&tstats_lock);
    + if (tstats_status == TSTATS_INACTIVE) {
    + tstats_status = TSTATS_RESET;
    + memset(tstats, 0, sizeof(tstats));
    + tstats_time = ktime_get();
    + tstats_status = TSTATS_ACTIVE;
    + }
    + spin_unlock_irq(&tstats_lock);
    + break;
    + default:
    + count = -EINVAL;
    + }
    +
    + 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 = seq_release,
    +};
    +
    +static int __init init_tstats(void)
    +{
    + struct proc_dir_entry *pe;
    +
    + pe = create_proc_entry("timer_stats", 0666, NULL);
    +
    + if (!pe)
    + return -ENOMEM;
    +
    + pe->proc_fops = &tstats_fops;
    +
    + return 0;
    +}
    +module_init(init_tstats);
    Index: linux-2.6.18-mm2/kernel/timer.c
    ===================================================================
    --- linux-2.6.18-mm2.orig/kernel/timer.c 2006-10-02 00:55:54.000000000 +0200
    +++ linux-2.6.18-mm2/kernel/timer.c 2006-10-02 00:55:55.000000000 +0200
    @@ -34,6 +34,7 @@
    #include <linux/cpu.h>
    #include <linux/syscalls.h>
    #include <linux/delay.h>
    +#include <linux/kallsyms.h>

    #include <asm/uaccess.h>
    #include <asm/unistd.h>
    @@ -133,6 +134,18 @@ static void internal_add_timer(tvec_base
    list_add_tail(&timer->entry, vec);
    }

    +#ifdef CONFIG_TIMER_STATS
    +void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
    +{
    + if (timer->start_site)
    + return;
    +
    + timer->start_site = addr;
    + memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
    + timer->start_pid = current->pid;
    +}
    +#endif
    +
    /**
    * init_timer - initialize a timer.
    * @timer: the timer to be initialized
    @@ -144,11 +157,16 @@ void fastcall init_timer(struct timer_li
    {
    timer->entry.next = NULL;
    timer->base = __raw_get_cpu_var(tvec_bases);
    +#ifdef CONFIG_TIMER_STATS
    + timer->start_site = NULL;
    + timer->start_pid = -1;
    + memset(timer->start_comm, 0, TASK_COMM_LEN);
    +#endif
    }
    EXPORT_SYMBOL(init_timer);

    static inline void detach_timer(struct timer_list *timer,
    - int clear_pending)
    + int clear_pending)
    {
    struct list_head *entry = &timer->entry;

    @@ -195,6 +213,7 @@ int __mod_timer(struct timer_list *timer
    unsigned long flags;
    int ret = 0;

    + timer_stats_timer_set_start_info(timer);
    BUG_ON(!timer->function);

    base = lock_timer_base(timer, &flags);
    @@ -245,6 +264,7 @@ void add_timer_on(struct timer_list *tim
    tvec_base_t *base = per_cpu(tvec_bases, cpu);
    unsigned long flags;

    + timer_stats_timer_set_start_info(timer);
    BUG_ON(timer_pending(timer) || !timer->function);
    spin_lock_irqsave(&base->lock, flags);
    timer->base = base;
    @@ -277,6 +297,7 @@ int mod_timer(struct timer_list *timer,
    {
    BUG_ON(!timer->function);

    + timer_stats_timer_set_start_info(timer);
    /*
    * This is a common optimization triggered by the
    * networking code - if the timer is re-modified
    @@ -307,6 +328,7 @@ int del_timer(struct timer_list *timer)
    unsigned long flags;
    int ret = 0;

    + timer_stats_timer_clear_start_info(timer);
    if (timer_pending(timer)) {
    base = lock_timer_base(timer, &flags);
    if (timer_pending(timer)) {
    @@ -440,6 +462,8 @@ static inline void __run_timers(tvec_bas
    fn = timer->function;
    data = timer->data;

    + timer_stats_account_timer(timer);
    +
    set_running_timer(base, timer);
    detach_timer(timer, 1);
    spin_unlock_irq(&base->lock);
    @@ -1119,7 +1143,8 @@ static void run_timer_softirq(struct sof
    {
    tvec_base_t *base = __get_cpu_var(tvec_bases);

    - hrtimer_run_queues();
    + hrtimer_run_queues();
    +
    if (time_after_eq(jiffies, base->timer_jiffies))
    __run_timers(base);
    }
    Index: linux-2.6.18-mm2/kernel/workqueue.c
    ===================================================================
    --- linux-2.6.18-mm2.orig/kernel/workqueue.c 2006-10-02 00:55:44.000000000 +0200
    +++ linux-2.6.18-mm2/kernel/workqueue.c 2006-10-02 00:55:55.000000000 +0200
    @@ -119,7 +119,7 @@ int fastcall queue_work(struct workqueue
    }
    EXPORT_SYMBOL_GPL(queue_work);

    -static void delayed_work_timer_fn(unsigned long __data)
    +void delayed_work_timer_fn(unsigned long __data)
    {
    struct work_struct *work = (struct work_struct *)__data;
    struct workqueue_struct *wq = work->wq_data;
    @@ -140,11 +140,12 @@ static void delayed_work_timer_fn(unsign
    * Returns non-zero if it was successfully added.
    */
    int fastcall queue_delayed_work(struct workqueue_struct *wq,
    - struct work_struct *work, unsigned long delay)
    + struct work_struct *work, unsigned long delay)
    {
    int ret = 0;
    struct timer_list *timer = &work->timer;

    + timer_stats_timer_set_start_info(&work->timer);
    if (!test_and_set_bit(0, &work->pending)) {
    BUG_ON(timer_pending(timer));
    BUG_ON(!list_empty(&work->entry));
    @@ -469,6 +470,7 @@ EXPORT_SYMBOL(schedule_work);
    */
    int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
    {
    + timer_stats_timer_set_start_info(&work->timer);
    return queue_delayed_work(keventd_wq, work, delay);
    }
    EXPORT_SYMBOL(schedule_delayed_work);
    Index: linux-2.6.18-mm2/lib/Kconfig.debug
    ===================================================================
    --- linux-2.6.18-mm2.orig/lib/Kconfig.debug 2006-10-02 00:55:44.000000000 +0200
    +++ linux-2.6.18-mm2/lib/Kconfig.debug 2006-10-02 00:55:55.000000000 +0200
    @@ -109,6 +109,17 @@ config SCHEDSTATS
    application, you can say N to avoid the very slight overhead
    this adds.

    +config TIMER_STATS
    + bool "Collect kernel timers statistics"
    + depends on DEBUG_KERNEL && PROC_FS
    + help
    + If you say Y here, additional code will be inserted into the
    + timer routines to collect statistics about kernel timers being
    + reprogrammed. The statistics can be read from /proc/tstats.
    + The statistics collection is started by writing 1 to /proc/tstats,
    + writing 0 stops it. This feature is useful to collect information
    + about timer usage patterns in kernel and userspace.
    +
    config DEBUG_SLAB
    bool "Debug slab memory allocations"
    depends on DEBUG_KERNEL && SLAB
    Index: linux-2.6.18-mm2/Documentation/hrtimer/timer_stats.txt
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-2.6.18-mm2/Documentation/hrtimer/timer_stats.txt 2006-10-02 00:55:55.000000000 +0200
    @@ -0,0 +1,68 @@
    +timer_stats - timer usage statistics
    +------------------------------------
    +
    +timer_stats is a debugging facility to make the timer (ab)usage in a Linux
    +system visible to kernel and userspace developers. It is not intended for
    +production usage as it adds significant overhead to the (hr)timer code and the
    +(hr)timer data structures.
    +
    +timer_stats should be used by kernel and userspace developers to verify that
    +their code does not make unduly use of timers. This helps to avoid unnecessary
    +wakeups, which should be avoided to optimize power consumption.
    +
    +It can be enabled by CONFIG_TIMER_STATS in the "Kernel hacking" configuration
    +section.
    +
    +timer_stats collects information about the timer events which are fired in a
    +Linux system over a sample period:
    +
    +- the pid of the task(process) which initialized the timer
    +- the name of the process which initialized the timer
    +- the function where the timer was intialized
    +- the callback function which is associated to the timer
    +- the number of events (callbacks)
    +
    +timer_stats adds an entry to /proc: /proc/timer_stats
    +
    +This entry is used to control the statistics functionality and to read out the
    +sampled information.
    +
    +The timer_stats functionality is inactive on bootup.
    +
    +To activate a sample period issue:
    +# echo 1 >/proc/timer_stats
    +
    +To stop a sample period issue:
    +# echo 0 >/proc/timer_stats
    +
    +The statistics can be retrieved by:
    +# cat /proc/timer_stats
    +
    +The readout of /proc/timer_stats automatically disables sampling. The sampled
    +information is kept until a new sample period is started. This allows multiple
    +readouts.
    +
    +Sample output of /proc/timer_stats:
    +
    +Timerstats sample period: 3.888770 s
    + 12, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
    + 15, 1 swapper hcd_submit_urb (rh_timer_func)
    + 4, 959 kedac schedule_timeout (process_timeout)
    + 1, 0 swapper page_writeback_init (wb_timer_fn)
    + 28, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
    + 22, 2948 IRQ 4 tty_flip_buffer_push (delayed_work_timer_fn)
    + 3, 3100 bash schedule_timeout (process_timeout)
    + 1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
    + 1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
    + 1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
    + 1, 2292 ip __netdev_watchdog_up (dev_watchdog)
    + 1, 23 events/1 do_cache_clean (delayed_work_timer_fn)
    +90 total events, 30.0 events/sec
    +
    +The first column is the number of events, the second column the pid, the third
    +column is the name of the process. The forth column shows the function which
    +initialized the timer and in parantheses the callback function which was
    +executed on expiry.
    +
    + Thomas, Ingo
    +
    --

    -
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