Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 02/10] nohz: Kick full dynticks timer targets with an empty IPI | Date | Mon, 28 Jul 2014 19:37:28 +0200 |
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While we enqueue a new timer on a dynticks target, we must send it an IPI so that it reschedules the next tick accordingly.
Now all we need for that is to run irq_exit() on the target. Hence an empty IRQ is way enough. We don't need to run tick_nohz_full_check() and all the overhead that comes with the several cmpxchg() necessary for irq work list and state progress.
So lets use a void irq work instead.
Cc: Ingo Molnar <mingo@kernel.org> Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> --- kernel/sched/core.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7f3063c..171f9ce 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -685,15 +685,13 @@ static void wake_up_idle_cpu(int cpu) static bool wake_up_full_nohz_cpu(int cpu) { /* - * We just need the target to call irq_exit() and re-evaluate - * the next tick. The nohz full kick at least implies that. - * If needed we can still optimize that later with an - * empty IRQ. + * Kick the target to make it call irq_exit() and re-evaluate + * the next tick. */ if (tick_nohz_full_cpu(cpu)) { if (cpu != smp_processor_id() || tick_nohz_tick_stopped()) - tick_nohz_full_kick_cpu(cpu); + kick_cpu_async(cpu); return true; } -- 1.8.3.1
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