From patchwork Tue Jul 18 13:41:20 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Aaron Lu X-Patchwork-Id: 122053 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:c923:0:b0:3e4:2afc:c1 with SMTP id j3csp1764450vqt; Tue, 18 Jul 2023 06:58:40 -0700 (PDT) X-Google-Smtp-Source: APBJJlEHSrUANGvIlF+mHaOtLOtNZNuAKQ/qfPLqENCbLpgb7/osI1UHj0MVhrInIKuIl8T4z+Nv X-Received: by 2002:a05:6512:3d0a:b0:4f9:58bd:9e5a with SMTP id d10-20020a0565123d0a00b004f958bd9e5amr11348916lfv.27.1689688719886; Tue, 18 Jul 2023 06:58:39 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1689688719; cv=none; d=google.com; s=arc-20160816; b=wvx2rQ0Ya/K29aarRXegUzFUkoWsJ5U56dCU8fsP61eYrfZw2S4XtZ63kGOguKpauI ook9wYoPfpjK833pRNBbuQo3Jq5CL4YGaZvY319A3mlpW1v+ZDfUCOJ0tl9RixmBE8pQ dFwsCgHR5K0AYB6wQKEWoZ1syPw1BuNZp90BrCl755W/QsvgtKz+GJLhIuFT19Lw92cb U0h7dYPKnP1TatrlFqD0FK8I5cuk/X2zmKRyk+/qfXuG8tZTsO5n2ihqQlp1dHUxhwwe gBh1SUPWpxuS6sqoNts/XDTkI4RkTpcvNaBQYLmLQsAewpntx4kVUmeEIPyWg2IE1Ghj bevQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=dLEJSQXLYoyH/3vNUMkFIUFC5iP4YNzi6WzwzckycYU=; fh=4ed2R7g6IAKyDvVc8idVdT+eA7jXSko9FHhVHVAkWGU=; b=MW7q0haO387kT6TrVncmXbsnJaYUWXKwEFjLiJstjR0Uodvin8CXaK6GAPwmzMCT2A Ak+ls4bQJTU8tobfio0Z+ACGTGkRQLtVhebGLQaUdagIugzZGCVs51L4AkV3Ut+QwmrS Y9OaJrZNvWLvffZHiAiBV1RPnw8zAcC6Juv8/K+/OgrXrWAMIHYmoWC8BG1UJwg1DwK6 wYhbq1FkluZfobxOWrg4TwlMcdEyyKLror6/58Q5FJ6SzSQq1Dp57wEhcbo3xqytcayq VC3oDgKlsr782G1bF1SnXom1V0DQL+VW2fJkZYd4+wqmVGqNIa1Kwx5mKzKWh+crUkoP NJcQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=nMby4OYa; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id s22-20020a170906bc5600b009925144d755si1199902ejv.461.2023.07.18.06.58.15; Tue, 18 Jul 2023 06:58:39 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=nMby4OYa; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232841AbjGRNl5 (ORCPT + 99 others); Tue, 18 Jul 2023 09:41:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232842AbjGRNlv (ORCPT ); Tue, 18 Jul 2023 09:41:51 -0400 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBCCB10CB for ; Tue, 18 Jul 2023 06:41:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1689687705; x=1721223705; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=RlvrBHFv6Du1879kI3EewacCpf6aQLiFMk7QITrDmtI=; b=nMby4OYaq5z4sAqoYkF7fAxD+rCs82nCNQZ37ezW1tsU3sCqUI5qgKbI d40NPZQeZ67rfWrZ1cU3yqLBNKG/uuos/9kREzD33CQlwVQZSLuFG9Cw1 Dju5Hk5m9FwOD1ATHrYFZl/AYJ9g65ggsh1uKnFsJo4sWTJPhCtqYyLNF TggZAVw1/AEvoaTwh9bclrb5t0yENWZApvPpj76u6melQzVVyjGZD4M6k avAwnEm2a/2igRB0Bc75/fSo7fb2o3bnu8vJ/jPesoC+TuvX5Y1mk44KG oM/8shn33G+n/5fqW8kt0noqIXUdKaQS6iGl+0KfcOqwnrCJr2CHBuJtU g==; X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="345800745" X-IronPort-AV: E=Sophos;i="6.01,214,1684825200"; d="scan'208";a="345800745" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2023 06:41:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="847706545" X-IronPort-AV: E=Sophos;i="6.01,214,1684825200"; d="scan'208";a="847706545" Received: from ziqianlu-desk2.sh.intel.com ([10.239.159.54]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2023 06:41:41 -0700 From: Aaron Lu To: Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Daniel Jordan Cc: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Tim Chen , Nitin Tekchandani , Yu Chen , Waiman Long , linux-kernel@vger.kernel.org Subject: [RFC PATCH 4/4] sched/fair: skip some update_cfs_group() on en/dequeue_entity() Date: Tue, 18 Jul 2023 21:41:20 +0800 Message-ID: <20230718134120.81199-5-aaron.lu@intel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230718134120.81199-1-aaron.lu@intel.com> References: <20230718134120.81199-1-aaron.lu@intel.com> MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_PASS,SPF_NONE,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1771767038633718310 X-GMAIL-MSGID: 1771767038633718310 After the previous patch, the cost of update_cfs_group() and update_load_avg() has dropped to around 1% for postgres_sysbench on SPR but netperf/UDP_RR on SPR still saw ~20% update_cfs_group() and ~10% update_load_avg() so this patch is another attempt to further reduce the two functions' cost from read side. The observation is: if an entity is dequeued, updating its weight isn't useful, except that the current code will also update its cfs_rq's load_avg using the updated weight...so removing update_cfs_group() on dequeue path can reduce cost of accessing tg->load_avg, but it also will reduce the tracking accuracy. Another hint I got from an ancient commit 17bc14b767cf("Revert "sched: Update_cfs_shares at period edge") is: if an entity is enqueued and it's the only entity of its cfs_rq, we do not need immediately update its weight since it's not needed to decide if it can preempt curr. commit 17bc14b767cf mentioned a latency problem when reducing calling frequency of update_cfs_group(): doing a make -j32 in one terminal window will cause browsing experience worse. To see how things are now, I did a test: two cgroups were created under root and in one group, I did "make -j32" and in the meantime, I did "./schbench -m 1 -t 6 -r 300" in another group on a 6core/12cpus Intel i7-8700T Coffee lake cpu and the wakeup latency reported by schbench for base and this series doesn't look much different: base: schbench -m 1 -t 6 -r 300: Latency percentiles (usec) runtime 300 (s) (18534 total samples) 50.0th: 20 (9491 samples) 75.0th: 25 (4768 samples) 90.0th: 29 (2552 samples) 95.0th: 62 (809 samples) *99.0th: 20320 (730 samples) 99.5th: 23392 (92 samples) 99.9th: 31392 (74 samples) min=6, max=32032 make -j32: real 5m35.950s user 47m33.814s sys 4m45.470s this series: schbench -m 1 -t 6 -r 300: Latency percentiles (usec) runtime 300 (s) (18528 total samples) 50.0th: 21 (9920 samples) 75.0th: 26 (4756 samples) 90.0th: 30 (2100 samples) 95.0th: 63 (846 samples) *99.0th: 19040 (722 samples) 99.5th: 21920 (92 samples) 99.9th: 30048 (81 samples) min=6, max=34873 make -j32: real 5m35.185s user 47m28.528s sys 4m44.705s As for netperf/UDP_RR/nr_thread=100% on SPR: after this change, the two functions' cost dropped to ~2%. Other test results: ================================================ postgres_sysbench(transaction, higher is better) nr_thread=100%/75%/50% were tested on 2 sockets SPR and Icelake and results that have a measuable difference are: nr_thread=100% on SPR: base: 90569.11±1.15% node: 104152.26±0.34% +15.0% delay: 127309.46±4.25% +40.6% skip: 125501.96±1.83% +38.6% nr_thread=75% on SPR: base: 100803.96±0.57% node: 107333.58±0.44% +6.5% delay: 124332.39±0.51% +23.3% skip: 127676.55±0.03% +26.7% nr_thread=75% on ICL: base: 61961.26±0.41% node: 61585.45±0.50% delay: 72420.52±0.14% +16.9% skip: 72413.23±0.30% +16.9% ======================================================================= hackbench/pipe/threads/fd=20/loop=1000000 (throughput, higher is better) group=1/4/8/16 were tested on 2 sockets SPR and Cascade lake and the results that have a measuable difference are: group=8 on SPR: base: 437163±2.6% node: 471203±1.2% +7.8% delay: 490780±0.9% +12.3% skip: 493062±1.9% +12.8% group=16 on SPR: base: 468279±1.9% node: 580385±1.7% +23.9% delay: 664422±0.2% +41.9% skip: 697387±0.2% +48.9% ================================================ netperf/TCP_STRAM (throughput, higher is better) nr_thread=1/25%/50%/75%/100% were tested on 2 sockets SPR and Cascade Lake and results that have measuable difference are: nr_thread=50% on SPR: base: 16258±0.7% node: 16172±2.9% delay: 17729±0.7% +9.0% skip: 17823±1.3% +9.6% nr_thread=75% on CSL: base: 12923±1.2% node: 13011±2.2% delay: 15452±1.6% +19.6% skip: 15302±1.7% +18.4% nr_thread=75% on SPR: base: 16232±11.9% node: 13962±5.1% delay: 21089±0.8% +29.9% skip: 21251±0.4% +30.9% nr_thread=100% on SPR: base: 13220±0.6% node: 13113±0.0% delay: 18258±11.3% +38.1% skip: 16974±12.7% +28.4% ============================================= netperf/UDP_RR (throughput, higher is better) nr_thread=1/25%/50%/75%/100% were tested on 2 sockets SPR and Cascade Lake and results that have measuable difference are: nr_thread=25% on CSL: base: 107269±0.3% node: 107226±0.2% delay: 106978±0.3% skip: 109652±0.3% +2.2% nr_thread=50% on CSL: base: 74854±0.1% node: 74521±0.4% delay: 74438±0.2% skip: 76431±0.1% +2.1% nr_thread=75% on CSL: base: 36701±1.7% node: 39949±1.4% +8.8% delay: 42516±0.3% +15.8% skip: 45044±0.5% +22.7% nr_thread=75% on SPR: base: 14249±3.8% node: 19890±2.0% +39.6% delay: 31331±0.5% +119.9% skip: 33688±3.5% +136.4% nr_thread=100% on CSL: base: 52275±0.6% node: 53827±0.4% +3.0% delay: 78386±0.7% +49.9% skip: 76926±2.3% +47.2% nr_thread=100% on SPR: base: 9560±1.6% node: 14186±3.9% +48.4% delay: 20779±2.8% +117.4% skip: 32125±2.5% +236.0% Signed-off-by: Aaron Lu --- kernel/sched/fair.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 564ffe3e59c1..0dbbb92302ad 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4862,7 +4862,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) */ update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH); se_update_runnable(se); - update_cfs_group(se); + if (cfs_rq->nr_running > 0) + update_cfs_group(se); account_entity_enqueue(cfs_rq, se); if (flags & ENQUEUE_WAKEUP) @@ -4978,8 +4979,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) /* return excess runtime on last dequeue */ return_cfs_rq_runtime(cfs_rq); - update_cfs_group(se); - /* * Now advance min_vruntime if @se was the entity holding it back, * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be