From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04FBAC433F5 for ; Thu, 28 Oct 2021 23:25:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D91EE60551 for ; Thu, 28 Oct 2021 23:25:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231490AbhJ1X1t (ORCPT ); Thu, 28 Oct 2021 19:27:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231431AbhJ1X1s (ORCPT ); Thu, 28 Oct 2021 19:27:48 -0400 Received: from mail-qk1-x72d.google.com (mail-qk1-x72d.google.com [IPv6:2607:f8b0:4864:20::72d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66CE9C061570 for ; Thu, 28 Oct 2021 16:25:20 -0700 (PDT) Received: by mail-qk1-x72d.google.com with SMTP id bl14so7576360qkb.4 for ; Thu, 28 Oct 2021 16:25:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=rBiiWNa3p59UclXi3y2/WqGDR5bPESvpDE52/45tevQ=; b=uXaadR9zViKfRg2SJgNwLjApdku+IzRMoVY0+E1N2Il4deyvpMzL4qF5ObxH3VUknA VZHPw6l52ycVeTfcglMz7QIuyjrDuCKAIpVCO20LLvN3LF+7ZObGKbYGCcCcvPkYlxQV TmFkfcEmX7a4PeW1bpzIbSbdf0B0k7mDfrWW0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=rBiiWNa3p59UclXi3y2/WqGDR5bPESvpDE52/45tevQ=; b=t43OFOu91/v1SDONC04rOsYjuwvRGW6DR/46oZpKKlUjEJ6ZG/0ZVDadF8aWxW1ttj VAT9888lRLYdfCr6OV4ww6KDXnekLK4Ub0dfxtOPvHGaeiiDfQ0ziERDo3/agxJpE/dx iXa8T0ydc92iYAwfriL2xNLlg5WrMemjk4l5/xwzfGp4puxLtlwvsrBoOHhac2ZQYUUo IbUhvsuidHgZPacH5yfCSxeZ7P+kZ1dbwqzkDlH3jc/8hyvHJz3V06HxxZG85e8UI5Lz /uJWYnFQaXyB1aj6WIodV5FJWVZ/UlAPeHuABuRQl9/Z3c+lQ+D8KHR242ZHRuIByZtb 181Q== X-Gm-Message-State: AOAM533J3xDLM95P6h6+B/O+MD64qk/w261BIHYxwqH3d6qaFz7Xr5lq +kIxZsHCpSoAtfSNwhKmePnI/g== X-Google-Smtp-Source: ABdhPJz0TrDC+NSbBTekEDO37Fd437XYYesWTOj1cwdWFxB+PndSnYRz7EKlhG66fWQUQqmmwqOxQw== X-Received: by 2002:a05:620a:24d1:: with SMTP id m17mr6170104qkn.316.1635463519460; Thu, 28 Oct 2021 16:25:19 -0700 (PDT) Received: from localhost ([2620:15c:6:411:64bf:5857:794e:a32b]) by smtp.gmail.com with ESMTPSA id bs33sm2961098qkb.130.2021.10.28.16.25.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Oct 2021 16:25:19 -0700 (PDT) Date: Thu, 28 Oct 2021 19:25:18 -0400 From: Joel Fernandes To: Vincent Guittot Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org, tim.c.chen@linux.intel.com, joelaf@google.com, dianders@google.com, qais.yousef@arm.com, Chris.Redpath@arm.com Subject: Re: [PATCH v3 0/5] Improve newidle lb cost tracking and early abort Message-ID: References: <20211019123537.17146-1-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211019123537.17146-1-vincent.guittot@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Vincent, Peter, On Tue, Oct 19, 2021 at 02:35:32PM +0200, Vincent Guittot wrote: > This patchset updates newidle lb cost tracking and early abort: > > The time spent running update_blocked_averages is now accounted in the 1st > sched_domain level. This time can be significant and move the cost of > newidle lb above the avg_idle time. > > The decay of max_newidle_lb_cost is modified to start only when the field > has not been updated for a while. Recent update will not be decayed > immediatlybut only after a while. > > The condition of an avg_idle lower than sysctl_sched_migration_cost has > been removed as the 500us value is quite large and prevent opportunity to > pull task on the newly idle CPU for at least 1st domain levels. It appears this series is not yet in upstream Linus's tree. What's the latest on it? I see a lot of times on ARM64 devices that load balance is skipped due to the high the sysctl_sched_migration_cost. I saw another thread as well where someone complained the performance varies and the default might be too high: https://lkml.org/lkml/2021/9/14/150 Any other thoughts? Happy to help on any progress on this series as well. Thanks, - Joel > > Monitoring sd->max_newidle_lb_cost on cpu0 of a Arm64 system > THX2 (2 nodes * 28 cores * 4 cpus) during the benchmarks gives the > following results: > min avg max > SMT: 1us 33us 273us - this one includes the update of blocked load > MC: 7us 49us 398us > NUMA: 10us 45us 158us > > > Some results for hackbench -l $LOOPS -g $group : > group tip/sched/core + this patchset > 1 15.189(+/- 2%) 14.987(+/- 2%) +1% > 4 4.336(+/- 3%) 4.322(+/- 5%) +0% > 16 3.654(+/- 1%) 2.922(+/- 3%) +20% > 32 3.209(+/- 1%) 2.919(+/- 3%) +9% > 64 2.965(+/- 1%) 2.826(+/- 1%) +4% > 128 2.954(+/- 1%) 2.993(+/- 8%) -1% > 256 2.951(+/- 1%) 2.894(+/- 1%) +2% > > tbench and reaim have not shown any difference > > Change since v2: > - Update and decay of sd->last_decay_max_lb_cost are gathered in > update_newidle_cost(). The behavior remains almost the same except that > the decay can happen during newidle_balance now. > > Tests results haven't shown any differences > > I haven't modified rq->max_idle_balance_cost. It acts as the max value > for avg_idle and prevents the latter to reach high value during long > idle phase. Moving on an IIR filter instead, could delay the convergence > of avg_idle to a reasonnable value that reflect current situation. > > - Added a minor cleanup of newidle_balance > > Change since v1: > - account the time spent in update_blocked_averages() in the 1st domain > > - reduce number of call of sched_clock_cpu() > > - change the way max_newidle_lb_cost is decayed. Peter suggested to use a > IIR but keeping a track of the current max value gave the best result > > - removed the condition (this_rq->avg_idle < sysctl_sched_migration_cost) > as suggested by Peter > > Vincent Guittot (5): > sched/fair: Account update_blocked_averages in newidle_balance cost > sched/fair: Skip update_blocked_averages if we are defering load > balance > sched/fair: Wait before decaying max_newidle_lb_cost > sched/fair: Remove sysctl_sched_migration_cost condition > sched/fair: cleanup newidle_balance > > include/linux/sched/topology.h | 2 +- > kernel/sched/fair.c | 65 ++++++++++++++++++++++------------ > kernel/sched/topology.c | 2 +- > 3 files changed, 45 insertions(+), 24 deletions(-) > > -- > 2.17.1 >