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Date: Wed, 24 Jun 2009 09:47:08 GMT
From: tip-bot for Heiko Carstens <heiko.carstens@...ibm.com>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
schwidefsky@...ibm.com, arjan@...radead.org,
akpm@...ux-foundation.org, mustafa.mesanovic@...ibm.com,
heiko.carstens@...ibm.com, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:timers/urgent] timer stats: Optimize by adding quick check to avoid function calls
Commit-ID: 507e123151149e578c9aae33eb876c49824da5f8
Gitweb: http://git.kernel.org/tip/507e123151149e578c9aae33eb876c49824da5f8
Author: Heiko Carstens <heiko.carstens@...ibm.com>
AuthorDate: Tue, 23 Jun 2009 17:38:15 +0200
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 24 Jun 2009 11:15:09 +0200
timer stats: Optimize by adding quick check to avoid function calls
When the kernel is configured with CONFIG_TIMER_STATS but timer
stats are runtime disabled we still get calls to
__timer_stats_timer_set_start_info which initializes some
fields in the corresponding struct timer_list.
So add some quick checks in the the timer stats setup functions
to avoid function calls to __timer_stats_timer_set_start_info
when timer stats are disabled.
In an artificial workload that does nothing but playing ping
pong with a single tcp packet via loopback this decreases cpu
consumption by 1 - 1.5%.
This is part of a modified function trace output on SLES11:
perl-2497 [00] 28630647177732388 [+ 125]: sk_reset_timer <-tcp_v4_rcv
perl-2497 [00] 28630647177732513 [+ 125]: mod_timer <-sk_reset_timer
perl-2497 [00] 28630647177732638 [+ 125]: __timer_stats_timer_set_start_info <-mod_timer
perl-2497 [00] 28630647177732763 [+ 125]: __mod_timer <-mod_timer
perl-2497 [00] 28630647177732888 [+ 125]: __timer_stats_timer_set_start_info <-__mod_timer
perl-2497 [00] 28630647177733013 [+ 93]: lock_timer_base <-__mod_timer
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Mustafa Mesanovic <mustafa.mesanovic@...ibm.com>
Cc: Arjan van de Ven <arjan@...radead.org>
LKML-Reference: <20090623153811.GA4641@...ris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
include/linux/hrtimer.h | 5 +++++
include/linux/timer.h | 4 ++++
kernel/time/timer_stats.c | 16 ++++++++--------
kernel/timer.c | 2 ++
4 files changed, 19 insertions(+), 8 deletions(-)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 7400900..54648e6 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -21,6 +21,7 @@
#include <linux/list.h>
#include <linux/wait.h>
#include <linux/percpu.h>
+#include <linux/timer.h>
struct hrtimer_clock_base;
@@ -447,6 +448,8 @@ extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
{
+ if (likely(!timer->start_pid))
+ return;
timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
timer->function, timer->start_comm, 0);
}
@@ -456,6 +459,8 @@ extern void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer,
static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
{
+ if (likely(!timer_stats_active))
+ return;
__timer_stats_hrtimer_set_start_info(timer, __builtin_return_address(0));
}
diff --git a/include/linux/timer.h b/include/linux/timer.h
index ccf882e..be62ec2 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -190,6 +190,8 @@ extern unsigned long get_next_timer_interrupt(unsigned long now);
*/
#ifdef CONFIG_TIMER_STATS
+extern int timer_stats_active;
+
#define TIMER_STATS_FLAG_DEFERRABLE 0x1
extern void init_timer_stats(void);
@@ -203,6 +205,8 @@ extern void __timer_stats_timer_set_start_info(struct timer_list *timer,
static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
{
+ if (likely(!timer_stats_active))
+ return;
__timer_stats_timer_set_start_info(timer, __builtin_return_address(0));
}
diff --git a/kernel/time/timer_stats.c b/kernel/time/timer_stats.c
index c994530..4cde8b9 100644
--- a/kernel/time/timer_stats.c
+++ b/kernel/time/timer_stats.c
@@ -96,7 +96,7 @@ static DEFINE_MUTEX(show_mutex);
/*
* Collection status, active/inactive:
*/
-static int __read_mostly active;
+int __read_mostly timer_stats_active;
/*
* Beginning/end timestamps of measurement:
@@ -242,7 +242,7 @@ void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
struct entry *entry, input;
unsigned long flags;
- if (likely(!active))
+ if (likely(!timer_stats_active))
return;
lock = &per_cpu(lookup_lock, raw_smp_processor_id());
@@ -254,7 +254,7 @@ void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
input.timer_flag = timer_flag;
spin_lock_irqsave(lock, flags);
- if (!active)
+ if (!timer_stats_active)
goto out_unlock;
entry = tstat_lookup(&input, comm);
@@ -290,7 +290,7 @@ static int tstats_show(struct seq_file *m, void *v)
/*
* If still active then calculate up to now:
*/
- if (active)
+ if (timer_stats_active)
time_stop = ktime_get();
time = ktime_sub(time_stop, time_start);
@@ -368,18 +368,18 @@ static ssize_t tstats_write(struct file *file, const char __user *buf,
mutex_lock(&show_mutex);
switch (ctl[0]) {
case '0':
- if (active) {
- active = 0;
+ if (timer_stats_active) {
+ timer_stats_active = 0;
time_stop = ktime_get();
sync_access();
}
break;
case '1':
- if (!active) {
+ if (!timer_stats_active) {
reset_entries();
time_start = ktime_get();
smp_mb();
- active = 1;
+ timer_stats_active = 1;
}
break;
default:
diff --git a/kernel/timer.c b/kernel/timer.c
index 54d3912..0b36b9e 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -380,6 +380,8 @@ static void timer_stats_account_timer(struct timer_list *timer)
{
unsigned int flag = 0;
+ if (likely(!timer->start_site))
+ return;
if (unlikely(tbase_get_deferrable(timer->base)))
flag |= TIMER_STATS_FLAG_DEFERRABLE;
--
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