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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93AEDC433E0 for ; Wed, 1 Jul 2020 16:32:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A67D20781 for ; Wed, 1 Jul 2020 16:32:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732414AbgGAQcQ (ORCPT ); Wed, 1 Jul 2020 12:32:16 -0400 Received: from foss.arm.com ([217.140.110.172]:55902 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731770AbgGAQcP (ORCPT ); Wed, 1 Jul 2020 12:32:15 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9D41431B; Wed, 1 Jul 2020 09:32:14 -0700 (PDT) Received: from [10.37.12.71] (unknown [10.37.12.71]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6F8133F68F; Wed, 1 Jul 2020 09:32:11 -0700 (PDT) Subject: Re: [PATCH v6 0/2] sched: Optionally skip uclamp logic in fast path To: Qais Yousef Cc: Ingo Molnar , Peter Zijlstra , Valentin Schneider , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Patrick Bellasi , Chris Redpath , linux-kernel@vger.kernel.org References: <20200630112123.12076-1-qais.yousef@arm.com> From: Lukasz Luba Message-ID: Date: Wed, 1 Jul 2020 17:32:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200630112123.12076-1-qais.yousef@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Qais, On 6/30/20 12:21 PM, Qais Yousef wrote: > This series attempts to address the report that uclamp logic could be expensive > sometimes and shows a regression in netperf UDP_STREAM under certain > conditions. > > The first patch is a fix for how struct uclamp_rq is initialized which is > required by the 2nd patch which contains the real 'fix'. > > Worth noting that the root cause of the overhead is believed to be system > specific or related to potential certain code/data layout issues, leading to > worse I/D $ performance. > > Different systems exhibited different behaviors and the regression did > disappear in certain kernel version while attempting to reporoduce. > > More info can be found here: > > https://lore.kernel.org/lkml/20200616110824.dgkkbyapn3io6wik@e107158-lin/ > > Having the static key seemed the best thing to do to ensure the effect of > uclamp is minimized for kernels that compile it in but don't have a userspace > that uses it, which will allow distros to distribute uclamp capable kernels by > default without having to compromise on performance for some systems that could > be affected. > > Changes in v6: > * s/uclamp_is_enabled/uclamp_is_used/ + add comment > * Improve the bailout condition for the case where we could end up with > unbalanced call of uclamp_rq_dec_id() > * Clarify some comments. > I've tried this v6 series with mmtest netperf-udp (30x each UDP size) - the results are good. v5.7-rc7-base-noucl v5.7-rc7-ucl-tsk-nofix v5.7-rc7-ucl-tsk-grp-fix_v6 Hmean send-64 62.15 ( 0.00%) 59.65 * -4.02%* 65.87 * 5.99%* Hmean send-128 122.88 ( 0.00%) 119.37 * -2.85%* 131.76 * 7.23%* Hmean send-256 244.85 ( 0.00%) 234.26 * -4.32%* 259.87 * 6.14%* Hmean send-1024 919.24 ( 0.00%) 880.67 * -4.20%* 975.48 * 6.12%* Hmean send-2048 1689.45 ( 0.00%) 1647.54 * -2.48%* 1797.23 * 6.38%* Hmean send-3312 2542.36 ( 0.00%) 2485.23 * -2.25%* 2665.69 * 4.85%* Hmean send-4096 2935.69 ( 0.00%) 2861.09 * -2.54%* 3087.79 * 5.18%* Hmean send-8192 4800.35 ( 0.00%) 4680.09 * -2.51%* 4966.50 * 3.46%* Hmean send-16384 7473.66 ( 0.00%) 7349.60 * -1.66%* 7598.49 * 1.67%* Hmean recv-64 62.15 ( 0.00%) 59.65 * -4.03%* 65.86 * 5.97%* Hmean recv-128 122.88 ( 0.00%) 119.37 * -2.85%* 131.76 * 7.23%* Hmean recv-256 244.84 ( 0.00%) 234.26 * -4.32%* 259.80 * 6.11%* Hmean recv-1024 919.24 ( 0.00%) 880.67 * -4.20%* 975.42 * 6.11%* Hmean recv-2048 1689.44 ( 0.00%) 1647.54 * -2.48%* 1797.18 * 6.38%* Hmean recv-3312 2542.36 ( 0.00%) 2485.23 * -2.25%* 2665.53 * 4.84%* Hmean recv-4096 2935.69 ( 0.00%) 2861.09 * -2.54%* 3087.79 * 5.18%* Hmean recv-8192 4800.35 ( 0.00%) 4678.15 * -2.55%* 4966.48 * 3.46%* Hmean recv-16384 7473.63 ( 0.00%) 7349.52 * -1.66%* 7597.90 * 1.66%* You can add: Tested-by: Lukasz Luba Regards, Lukasz