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[209.132.180.67]) by mx.google.com with ESMTP id sw1si2517446pab.112.2014.01.14.20.53.43; Tue, 14 Jan 2014 20:53:43 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751527AbaAOExi (ORCPT + 26 others); Tue, 14 Jan 2014 23:53:38 -0500 Received: from mail-pa0-f45.google.com ([209.85.220.45]:38486 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751042AbaAOExf (ORCPT ); Tue, 14 Jan 2014 23:53:35 -0500 Received: by mail-pa0-f45.google.com with SMTP id ld10so620649pab.32 for ; Tue, 14 Jan 2014 20:53:35 -0800 (PST) X-Received: by 10.68.166.69 with SMTP id ze5mr142450pbb.82.1389761615257; Tue, 14 Jan 2014 20:53:35 -0800 (PST) Received: from [10.0.0.100] ([162.243.130.63]) by mx.google.com with ESMTPSA id qq5sm4994125pbb.24.2014.01.14.20.53.29 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 14 Jan 2014 20:53:34 -0800 (PST) Message-ID: <52D61448.3070108@linaro.org> Date: Wed, 15 Jan 2014 12:53:28 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Michael wang , 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 Subject: Re: [RFC PATCH] sched: find the latest idle cpu References: <1389758879-19951-1-git-send-email-alex.shi@linaro.org> <52D60F11.3070005@linux.vnet.ibm.com> <52D61333.8060705@linaro.org> In-Reply-To: <52D61333.8060705@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: list List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: alex.shi@linaro.org X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 209.85.212.43 is neither permitted nor denied by best guess record for domain of patch+caf_=patchwork-forward=linaro.org@linaro.org) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org X-Google-Group-Id: 836684582541 List-Post: , List-Help: , List-Archive: List-Unsubscribe: , On 01/15/2014 12:48 PM, Alex Shi wrote: > On 01/15/2014 12:31 PM, Michael wang wrote: >> Hi, Alex >> >> On 01/15/2014 12:07 PM, Alex Shi wrote: >> [snip] } >>> +#ifdef CONFIG_NO_HZ_COMMON >>> + /* >>> + * Coarsely to get the latest idle cpu for shorter latency and >>> + * possible power benefit. >>> + */ >>> + if (!min_load) { > > here should be !load. >>> + struct tick_sched *ts = &per_cpu(tick_cpu_sched, i); >>> + >>> + s64 latest_wake = 0; >> >> I guess we missed some code for latest_wake here? > > Yes, thanks for reminder! > > so updated patch: > ops, still incorrect. re-updated: === >From 5d48303b3eb3b5ca7fde54a6dfcab79cff360403 Mon Sep 17 00:00:00 2001 From: Alex Shi Date: Tue, 14 Jan 2014 23:07:42 +0800 Subject: [PATCH] sched: find the latest idle cpu 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 | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c7395d9..e2c4cd9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4161,12 +4161,38 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) /* Traverse only the allowed CPUs */ for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { + s64 latest_wake = 0; + load = weighted_cpuload(i); if (load < min_load || (load == min_load && i == 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 (!load) { + struct tick_sched *ts = &per_cpu(tick_cpu_sched, i); + + /* 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 { + s64 temp = ktime_to_us(ts->idle_entrytime); + if (temp > latest_wake) { + latest_wake = temp; + idlest = i; + } + } + } +#endif } return idlest;