Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752531AbbF3OYF (ORCPT ); Tue, 30 Jun 2015 10:24:05 -0400 Received: from mail-ie0-f177.google.com ([209.85.223.177]:32828 "EHLO mail-ie0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751203AbbF3OX5 (ORCPT ); Tue, 30 Jun 2015 10:23:57 -0400 MIME-Version: 1.0 In-Reply-To: <1435157880-22925-9-git-send-email-riel@redhat.com> References: <1435157880-22925-1-git-send-email-riel@redhat.com> <1435157880-22925-9-git-send-email-riel@redhat.com> Date: Tue, 30 Jun 2015 17:23:56 +0300 Message-ID: Subject: Re: [RFC PATCH 08/11] nohz,timer: have housekeeper call account_process_tick for nohz cpus From: Frederic Weisbecker To: Rik van Riel Cc: LKML , Frederic Weisbecker , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Andy Lutomirski Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2990 Lines: 87 2015-06-24 17:57 GMT+03:00 : > From: Rik van Riel > > Have the housekeeper CPU call account_process_tick to do tick based > accounting for remote nohz_full CPUs. > > Signed-off-by: Rik van Riel > --- > kernel/time/timer.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/kernel/time/timer.c b/kernel/time/timer.c > index 2ece3aa5069c..6adebb373317 100644 > --- a/kernel/time/timer.c > +++ b/kernel/time/timer.c > @@ -42,6 +42,7 @@ > #include > #include > #include > +#include "../sched/sched.h" > > #include > #include > @@ -1382,6 +1383,29 @@ unsigned long get_next_timer_interrupt(unsigned long now) > } > #endif > > +#ifdef CONFIG_NO_HZ_FULL > +static void account_remote_process_ticks(void) > +{ > + int cpu; > + > + /* > + * The current task on another CPU can get rescheduled while > + * we are updating the statistics. The rcu read lock ensures > + * the task does not get freed, so at worst the statistics will > + * be off a little bit, which is expected with tick based sampling. > + */ > + rcu_read_lock(); > + for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask) { > + struct task_struct *p = cpu_curr(cpu); > + int user_tick = (per_cpu(context_tracking.state, cpu) == > + CONTEXT_USER); > + > + account_process_tick(p, user_tick); > + } > + rcu_read_unlock(); > +} > +#endif > + > /* > * Called from the timer interrupt handler to charge one tick to the current > * process. user_tick is 1 if the tick is user time, 0 for system. > @@ -1392,6 +1416,10 @@ void update_process_times(int user_tick) > > /* Note: this timer irq context must be accounted for as well. */ > account_process_tick(p, user_tick); > +#ifdef CONFIG_NO_HZ_FULL > + if (is_timer_housekeeping_cpu(smp_processor_id())) > + account_remote_process_ticks(); > +#endif I like the idea overall. I just think that it should be done from a process rather than an IRQ because the amount of CPUs to walk can be high. Perhaps a kthread? Or workqueue since we can now affine the unbound ones to housekeepers. Thanks. > run_local_timers(); > rcu_check_callbacks(user_tick); > #ifdef CONFIG_IRQ_WORK > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/