Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752233AbaBXCLJ (ORCPT ); Sun, 23 Feb 2014 21:11:09 -0500 Received: from mail-vc0-f181.google.com ([209.85.220.181]:64114 "EHLO mail-vc0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752000AbaBXCLH (ORCPT ); Sun, 23 Feb 2014 21:11:07 -0500 MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 24 Feb 2014 10:11:05 +0800 Message-ID: Subject: Re: [tip:sched/core] sched, nohz: Exclude isolated cores from load balancing From: Lei Wen To: mingo@kernel.org, hpa@zytor.com, mgalbraith@suse.de, linux-kernel@vger.kernel.org, peterz@infradead.org, leiwen@marvell.com, tglx@linutronix.de Cc: linux-tip-commits@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Feb 23, 2014 at 2:04 AM, tip-bot for Mike Galbraith wrote: > Commit-ID: d987fc7f3228bf94cb6b21313ebab1d64ee637ad > Gitweb: http://git.kernel.org/tip/d987fc7f3228bf94cb6b21313ebab1d64ee637ad > Author: Mike Galbraith > AuthorDate: Mon, 5 Dec 2011 10:01:47 +0100 > Committer: Ingo Molnar > CommitDate: Sat, 22 Feb 2014 18:17:22 +0100 > > sched, nohz: Exclude isolated cores from load balancing > > The user explicitly disabled load balancing, else this core would not be > disconnected. Don't add these to nohz.idle_cpus_mask. > > Signed-off-by: Mike Galbraith > Signed-off-by: Peter Zijlstra > Cc: Lei Wen > Link: http://lkml.kernel.org/n/tip-vmme4f49psirp966pklm5l9j@git.kernel.org > Signed-off-by: Thomas Gleixner > Signed-off-by: Ingo Molnar > --- > kernel/sched/fair.c | 25 ++++++++++++++++++------- > 1 file changed, 18 insertions(+), 7 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 7982faf..a3a41c61 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6788,6 +6788,11 @@ out_unlock: > return 0; > } > > +static inline int on_null_domain(struct rq *rq) > +{ > + return unlikely(!rcu_dereference_sched(rq->sd)); > +} > + > #ifdef CONFIG_NO_HZ_COMMON > /* > * idle load balancing details > @@ -6842,8 +6847,13 @@ static void nohz_balancer_kick(void) > static inline void nohz_balance_exit_idle(int cpu) > { > if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) { > - cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); > - atomic_dec(&nohz.nr_cpus); > + /* > + * Completely isolated CPUs don't ever set, so we must test. > + */ > + if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) { > + cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); How about use the API as cpumask_test_and_clear_cpu? Then below one line is enough. + if (likely(cpumask_test_and_clear_cpu(cpu, nohz.idle_cpus_mask))) { And I am not pretty sure whether we need such test here. Since if one cpu is set to NULL domain, it would not set NOHZ_TICK_STOPPED. And it would not enter into this logic. Unless that cpu is set to NULL domain when it already run after nohz_balance_enter_idle. Not sure what status would it be, and whether it could be set NULL domain then... > + atomic_dec(&nohz.nr_cpus); > + } > clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); > } > } > @@ -6897,6 +6907,12 @@ void nohz_balance_enter_idle(int cpu) > if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu))) > return; > > + /* > + * If we're a completely isolated CPU, we don't play. > + */ > + if (on_null_domain(cpu_rq(cpu))) > + return; > + Great! it is much better than my previous patch. > cpumask_set_cpu(cpu, nohz.idle_cpus_mask); > atomic_inc(&nohz.nr_cpus); > set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); > @@ -7159,11 +7175,6 @@ static void run_rebalance_domains(struct softirq_action *h) > nohz_idle_balance(this_rq, idle); > } > > -static inline int on_null_domain(struct rq *rq) > -{ > - return !rcu_dereference_sched(rq->sd); > -} > - > /* > * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. > */ > -- > 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/