From patchwork Wed Apr 19 16:29:30 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Guittot X-Patchwork-Id: 97646 Delivered-To: patch@linaro.org Received: by 10.140.109.52 with SMTP id k49csp402199qgf; Wed, 19 Apr 2017 09:30:11 -0700 (PDT) X-Received: by 10.36.116.205 with SMTP id o196mr4165180itc.96.1492619411789; Wed, 19 Apr 2017 09:30:11 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id e79si3627551itd.46.2017.04.19.09.30.11; Wed, 19 Apr 2017 09:30:11 -0700 (PDT) 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; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938028AbdDSQ37 (ORCPT + 16 others); Wed, 19 Apr 2017 12:29:59 -0400 Received: from mail-wm0-f53.google.com ([74.125.82.53]:35625 "EHLO mail-wm0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937931AbdDSQ34 (ORCPT ); Wed, 19 Apr 2017 12:29:56 -0400 Received: by mail-wm0-f53.google.com with SMTP id w64so84741318wma.0 for ; Wed, 19 Apr 2017 09:29:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=dge3D3CeqIqDw3RW+f2hjtV5/jF1+jne3naukSPrTbI=; b=jjvPfsncWXJZEsJ5MB1FijaXHGWGkNndv6mGAN6h7Yl6G989uHaeH6sDkcKlZt2d0N I1KQ/sY0l+SiFKiHqZvPYnPG1YjWFWJ0Z7fWjXk0o1lnBSxpZy/riIc2hQhk1D8Fg0PX yle61BcrBtOzrem6M0BRrV1GUrHiYsDc/5QeY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=dge3D3CeqIqDw3RW+f2hjtV5/jF1+jne3naukSPrTbI=; b=ccwV5r3VS16RiY6J2gNX3puy9z49CEPSJcrR+A6cI/B8DJdLeL0hO0pwq3Sni/EsVH 8XB4xDHPLMb8xyr1KRPWCL0BdVuEbt3HLLFHTgypWM0v2Dfzc5bUA5crk1eQ/oBMkACo kUzuBAq/polPjrm0otYxbq/nUH0foFBzNuiz0OfebWAjde26hWEvCnKSuKgDw4JYOVoN Irj101tV8GCPRQpDGhztInnFwUkLS0tN4Yrog2N42ADCHrWh+MZ/08fYo/6gZ1YV0eVN el4sQocvpe1BxC5aWCcRE29bBPqLZT5yr5cnJhXNfWWngaBAKkV1NuWbRf7wIoTOdvDe /UCg== X-Gm-Message-State: AN3rC/7QB7HKvGjj3azwTH/Hujqcv8429ZNuw/RPN7SUTx51OoaB5hQV kKyqFgEtQYtSexIa X-Received: by 10.28.234.205 with SMTP id g74mr19283911wmi.13.1492619383700; Wed, 19 Apr 2017 09:29:43 -0700 (PDT) Received: from localhost.localdomain ([2a01:e0a:f:6020:ddb5:fd5c:4a08:a3bc]) by smtp.gmail.com with ESMTPSA id o9sm4451536wmd.4.2017.04.19.09.29.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 19 Apr 2017 09:29:43 -0700 (PDT) From: Vincent Guittot To: mingo@kernel.org, linux-kernel@vger.kernel.org Cc: dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, yuyang.du@intel.com, pjt@google.com, bsegall@google.com, Vincent Guittot Subject: [PATCH 2/2] sched/cfs: take into account current time segment Date: Wed, 19 Apr 2017 18:29:30 +0200 Message-Id: <1492619370-29246-3-git-send-email-vincent.guittot@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1492619370-29246-1-git-send-email-vincent.guittot@linaro.org> References: <1492619370-29246-1-git-send-email-vincent.guittot@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To not consider the current time segment adds unwanted latency in the load/util_avg responsivness especially when the time is scaled instead of the contribution. Instead of waiting for the current time segment to have fully elapsed before accounting it in load/util_avg, we can already account the elapsed part but change the range used to compute load/util_avg accordingly. At the very beginning of a new time segment, the past segments have been decayed and the max value is MAX_LOAD_AVG*y. At the very end of the current time segment, the max value becomes 1024(us) + MAX_LOAD_AVG*y which is equal to MAX_LOAD_AVG. In fact, the max value is sa->period_contrib + MAX_LOAD_AVG*y at any time in the time segment. Taking advantage of the fact that MAX_LOAD_AVG*y == MAX_LOAD_AVG-1024, the range becomes [0..MAX_LOAD_AVG-1024+sa->period_contrib]. As the elapsed part is already accounted in load/util_sum, we update the max value according to the current position in the time segment instead of removing its contribution. Signed-off-by: Vincent Guittot --- kernel/sched/fair.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) -- 2.7.4 diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f74da94..c3b8f0f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3017,15 +3017,12 @@ ___update_load_avg(u64 now, int cpu, struct sched_avg *sa, /* * Step 2: update *_avg. */ - sa->load_avg = div_u64((sa->load_sum - sa->period_contrib * weight), - (LOAD_AVG_MAX - 1024)); + sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX - 1024 + sa->period_contrib); if (cfs_rq) { cfs_rq->runnable_load_avg = - div_u64((cfs_rq->runnable_load_sum - sa->period_contrib * weight), - (LOAD_AVG_MAX - 1024)); + div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX - 1024 + sa->period_contrib); } - sa->util_avg = (sa->util_sum - (running * sa->period_contrib << SCHED_CAPACITY_SHIFT)) / - (LOAD_AVG_MAX - 1024); + sa->util_avg = sa->util_sum / (LOAD_AVG_MAX - 1024 + sa->period_contrib); return 1; }