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 --- kernel/timer.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel/timer.c') diff --git a/kernel/timer.c b/kernel/timer.c index 54d3912f8ca..0b36b9e5cc8 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; -- cgit v1.2.3-70-g09d2 From 4841158b26e28e1476eed84c7347c18f11317750 Mon Sep 17 00:00:00 2001 From: Pavel Roskin Date: Sat, 18 Jul 2009 16:46:02 -0400 Subject: timer: Avoid reading uninitialized data timer->expires may be uninitialized, so check timer_pending() before touching timer->expires to pacify kmemcheck. Signed-off-by: Pavel Roskin LKML-Reference: <20090718204602.5191.360.stgit@mj.roinet.com> Signed-off-by: Thomas Gleixner --- kernel/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/timer.c') diff --git a/kernel/timer.c b/kernel/timer.c index 0b36b9e5cc8..a7f07d5a624 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -714,7 +714,7 @@ int mod_timer(struct timer_list *timer, unsigned long expires) * networking code - if the timer is re-modified * to be the same thing then just return: */ - if (timer->expires == expires && timer_pending(timer)) + if (timer_pending(timer) && timer->expires == expires) return 1; return __mod_timer(timer, expires, false, TIMER_NOT_PINNED); -- cgit v1.2.3-70-g09d2