Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751689AbaAOEIV (ORCPT ); Tue, 14 Jan 2014 23:08:21 -0500 Received: from mail-pa0-f43.google.com ([209.85.220.43]:45758 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751499AbaAOEIT (ORCPT ); Tue, 14 Jan 2014 23:08:19 -0500 From: Alex Shi To: mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, daniel.lezcano@linaro.org, vincent.guittot@linaro.org, morten.rasmussen@arm.com Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, fengguang.wu@intel.com, linaro-kernel@lists.linaro.org, Alex Shi Subject: [RFC PATCH] sched: find the latest idle cpu Date: Wed, 15 Jan 2014 12:07:59 +0800 Message-Id: <1389758879-19951-1-git-send-email-alex.shi@linaro.org> X-Mailer: git-send-email 1.8.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently we just try to find least load cpu. If some cpus idled, we just pick the first cpu in cpu mask. In fact we can get the interrupted idle cpu or the latest idled cpu, then we may get the benefit from both latency and power. The selected cpu maybe not the best, since other cpu may be interrupted during our selecting. But be captious costs too much. Signed-off-by: Alex Shi --- kernel/sched/fair.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c7395d9..fb52d26 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4167,6 +4167,26 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) min_load = load; idlest = i; } +#ifdef CONFIG_NO_HZ_COMMON + /* + * Coarsely to get the latest idle cpu for shorter latency and + * possible power benefit. + */ + if (!min_load) { + struct tick_sched *ts = &per_cpu(tick_cpu_sched, i); + + s64 latest_wake = 0; + /* idle cpu doing irq */ + if (ts->inidle && !ts->idle_active) + idlest = i; + /* the cpu resched */ + else if (!ts->inidle) + idlest = i; + /* find latest idle cpu */ + else if (ktime_to_us(ts->idle_entrytime) > latest_wake) + idlest = i; + } +#endif } return idlest; -- 1.8.1.2 -- 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/