From 507e123151149e578c9aae33eb876c49824da5f8 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Tue, 23 Jun 2009 17:38:15 +0200 Subject: 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 Cc: Andrew Morton Cc: Martin Schwidefsky Cc: Mustafa Mesanovic Cc: Arjan van de Ven LKML-Reference: <20090623153811.GA4641@osiris.boeblingen.de.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/hrtimer.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/hrtimer.h') diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 7400900de94a..54648e625efd 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -21,6 +21,7 @@ #include #include #include +#include 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)); } -- cgit v1.2.3 From f9f868dbcca961ed62f1df1d114abd0c38c47dce Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Thu, 9 Jul 2009 11:24:26 +0200 Subject: timer stats: fix quick check optimization git commit 507e1231 "timer stats: Optimize by adding quick check to avoid function calls" added one wrong check so that one unnecessary function call isn't elimated. time_stats_account_hrtimer() checks if timer->start_pid isn't initialized in order to find out if timer_stats_update_stats() should be called. However start_pid is initialized with -1 instead of 0, so that the function call always happens. Check timer->start_site like in timer_stats_account_timer() to fix this. Signed-off-by: Heiko Carstens Signed-off-by: Thomas Gleixner --- include/linux/hrtimer.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/hrtimer.h') diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 54648e625efd..4759917adc71 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -448,7 +448,7 @@ 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)) + if (likely(!timer->start_site)) return; timer_stats_update_stats(timer, timer->start_pid, timer->start_site, timer->function, timer->start_comm, 0); -- cgit v1.2.3