From 1f3b0f8243cb934307f59bd4d8e43b868e61d4d9 Mon Sep 17 00:00:00 2001 From: Gaurav Jindal Date: Thu, 14 Jul 2016 12:04:20 +0000 Subject: [PATCH] tick/nohz: Optimize nohz idle enter tick_nohz_start_idle is called before checking whether the idle tick can be stopped. If the tick cannot be stopped, calling tick_nohz_start_idle() is pointless and just wasting CPU cycles. Only invoke tick_nohz_start_idle() when can_stop_idle_tick() returns true. A short one minute observation of the effect on ARM64 shows a reduction of calls by 1.5% thus optimizing the idle entry sequence. [tglx: Massaged changelog ] Co-developed-by: Sanjeev Yadav Signed-off-by: Gaurav Jindal Link: http://lkml.kernel.org/r/20160714120416.GB21099@gaurav.jindal@spreadtrum.com Signed-off-by: Thomas Gleixner --- kernel/time/tick-sched.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 2ec7c00..204fdc8 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -908,11 +908,10 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts) ktime_t now, expires; int cpu = smp_processor_id(); - now = tick_nohz_start_idle(ts); - if (can_stop_idle_tick(cpu, ts)) { int was_stopped = ts->tick_stopped; + now = tick_nohz_start_idle(ts); ts->idle_calls++; expires = tick_nohz_stop_sched_tick(ts, now, cpu); -- 2.7.4