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authorHeiko Carstens <heiko.carstens@de.ibm.com>2009-06-23 17:38:15 +0200
committerIngo Molnar <mingo@elte.hu>2009-06-24 11:15:09 +0200
commit507e123151149e578c9aae33eb876c49824da5f8 (patch)
tree10b4c36a278553ed3814c0643442e7210a7a1a15 /include/linux/timer.h
parentbfdb4d9f0f611687d71cf6a460efc9e755f4a462 (diff)
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@de.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Mustafa Mesanovic <mustafa.mesanovic@de.ibm.com> Cc: Arjan van de Ven <arjan@infradead.org> LKML-Reference: <20090623153811.GA4641@osiris.boeblingen.de.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/timer.h')
-rw-r--r--include/linux/timer.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/timer.h b/include/linux/timer.h
index ccf882eed8f..be62ec2ebea 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));
}