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Subject[patch 44/46] Add debugging feature /proc/timer_stat
From: Ingo Molnar <mingo@elte.hu>

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/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec

[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

Documentation/hrtimer/timer_stats.txt | 68 +++++
include/linux/hrtimer.h | 45 +++
include/linux/timer.h | 55 ++++
kernel/hrtimer.c | 26 ++
kernel/time/Makefile | 1
kernel/time/timer_stats.c | 411 ++++++++++++++++++++++++++++++++++
kernel/timer.c | 31 ++
kernel/workqueue.c | 7
lib/Kconfig.debug | 11
9 files changed, 651 insertions(+), 4 deletions(-)

Index: linux-2.6.20-rc4-mm1-bo/Documentation/hrtimer/timer_stats.txt
===================================================================
--- /dev/null
+++ linux-2.6.20-rc4-mm1-bo/Documentation/hrtimer/timer_stats.txt
@@ -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
+
Index: linux-2.6.20-rc4-mm1-bo/include/linux/hrtimer.h
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/include/linux/hrtimer.h
+++ linux-2.6.20-rc4-mm1-bo/include/linux/hrtimer.h
@@ -119,6 +119,11 @@ 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
};

/**
@@ -311,4 +316,44 @@ extern unsigned long ktime_divns(const k
# define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
#endif

+/*
+ * 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_stats_hrtimer_set_start_info(struct hrtimer *timer)
+{
+}
+
+static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
+{
+}
+#endif
+
#endif
Index: linux-2.6.20-rc4-mm1-bo/include/linux/timer.h
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/include/linux/timer.h
+++ linux-2.6.20-rc4-mm1-bo/include/linux/timer.h
@@ -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 +79,55 @@ 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 init_timer_stats(void);
+
+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 init_timer_stats(void)
+{
+}
+
+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-2.6.20-rc4-mm1-bo/kernel/hrtimer.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/hrtimer.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/hrtimer.c
@@ -585,6 +585,18 @@ static inline void hrtimer_init_timer_hr

#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
+
/*
* Counterpart to lock_timer_base above:
*/
@@ -743,6 +755,7 @@ 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);
@@ -791,6 +804,8 @@ 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);
@@ -925,6 +940,12 @@ 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);

@@ -1006,6 +1027,7 @@ void hrtimer_interrupt(struct clock_even

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

/*
* Note: We clear the CALLBACK bit after
@@ -1050,6 +1072,8 @@ 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);
@@ -1106,6 +1130,8 @@ 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-2.6.20-rc4-mm1-bo/kernel/time/Makefile
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/time/Makefile
+++ linux-2.6.20-rc4-mm1-bo/kernel/time/Makefile
@@ -5,3 +5,4 @@ obj-$(CONFIG_GENERIC_CLOCKEVENTS) += ti
obj-$(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) += tick-broadcast.o
obj-$(CONFIG_TICK_ONESHOT) += tick-oneshot.o
obj-$(CONFIG_TICK_ONESHOT) += tick-sched.o
+obj-$(CONFIG_TIMER_STATS) += timer_stats.o
Index: linux-2.6.20-rc4-mm1-bo/kernel/time/timer_stats.c
===================================================================
--- /dev/null
+++ linux-2.6.20-rc4-mm1-bo/kernel/time/timer_stats.c
@@ -0,0 +1,411 @@
+/*
+ * 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;
+
+ /*
+ * 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:
+ */
+static int __read_mostly 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)
+
+unsigned long nr_entries;
+static struct entry entries[MAX_ENTRIES];
+
+static atomic_t overflow_count;
+
+static void reset_entries(void)
+{
+ nr_entries = 0;
+ memset(entries, 0, sizeof(entries));
+ atomic_set(&overflow_count, 0);
+}
+
+static struct entry *alloc_entry(void)
+{
+ if (nr_entries >= MAX_ENTRIES)
+ return NULL;
+
+ return entries + nr_entries++;
+}
+
+/*
+ * 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 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;
+ memcpy(curr->comm, comm, TASK_COMM_LEN);
+ if (prev)
+ prev->next = curr;
+ else
+ *head = curr;
+ curr->next = NULL;
+ }
+ 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)
+{
+ /*
+ * It doesnt matter which lock we take:
+ */
+ spinlock_t *lock = &per_cpu(lookup_lock, raw_smp_processor_id());
+ struct entry *entry, input;
+ unsigned long flags;
+
+ input.timer = timer;
+ input.start_func = startf;
+ input.expire_func = timerf;
+ input.pid = pid;
+
+ spin_lock_irqsave(lock, flags);
+ if (!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 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 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 (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: v0.1\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;
+ 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.%ld events/sec\n", events,
+ events / period.tv_sec, events * 1000 / ms);
+ 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 (active) {
+ active = 0;
+ time_stop = ktime_get();
+ sync_access();
+ }
+ break;
+ case '1':
+ if (!active) {
+ reset_entries();
+ time_start = ktime_get();
+ 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 = seq_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 = create_proc_entry("timer_stats", 0644, NULL);
+ if (!pe)
+ return -ENOMEM;
+
+ pe->proc_fops = &tstats_fops;
+
+ return 0;
+}
+__initcall(init_tstats_procfs);
Index: linux-2.6.20-rc4-mm1-bo/kernel/timer.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/timer.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/timer.c
@@ -35,6 +35,7 @@
#include <linux/syscalls.h>
#include <linux/delay.h>
#include <linux/tick.h>
+#include <linux/kallsyms.h>

#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -263,6 +264,18 @@ 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
@@ -274,11 +287,16 @@ 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;

@@ -325,6 +343,7 @@ 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);
@@ -375,6 +394,7 @@ 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;
@@ -407,6 +427,7 @@ 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
@@ -437,6 +458,7 @@ 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)) {
@@ -570,6 +592,8 @@ 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);
@@ -1229,7 +1253,8 @@ 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);
}
@@ -1675,6 +1700,8 @@ void __init init_timers(void)
int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
(void *)(long)smp_processor_id());

+ init_timer_stats();
+
BUG_ON(err == NOTIFY_BAD);
register_cpu_notifier(&timers_nb);
open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
Index: linux-2.6.20-rc4-mm1-bo/kernel/workqueue.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/workqueue.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/workqueue.c
@@ -218,7 +218,7 @@ 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 delayed_work *dwork = (struct delayed_work *)__data;
struct workqueue_struct *wq = get_wq_data(&dwork->work);
@@ -245,6 +245,7 @@ int fastcall queue_delayed_work(struct w
struct timer_list *timer = &dwork->timer;
struct work_struct *work = &dwork->work;

+ timer_stats_timer_set_start_info(timer);
if (delay == 0)
return queue_work(wq, work);

@@ -593,8 +594,10 @@ EXPORT_SYMBOL(schedule_work);
* After waiting for a given time this puts a job in the kernel-global
* workqueue.
*/
-int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
+int fastcall schedule_delayed_work(struct delayed_work *dwork,
+ unsigned long delay)
{
+ timer_stats_timer_set_start_info(&dwork->timer);
return queue_delayed_work(keventd_wq, dwork, delay);
}
EXPORT_SYMBOL(schedule_delayed_work);
Index: linux-2.6.20-rc4-mm1-bo/lib/Kconfig.debug
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/lib/Kconfig.debug
+++ linux-2.6.20-rc4-mm1-bo/lib/Kconfig.debug
@@ -125,6 +125,17 @@ 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/timer_stats.
+ The statistics collection is started by writing 1 to /proc/timer_stats,
+ 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
--

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