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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2139EC6FD1D for ; Mon, 20 Mar 2023 15:19:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232632AbjCTPTt (ORCPT ); Mon, 20 Mar 2023 11:19:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59320 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232576AbjCTPT3 (ORCPT ); Mon, 20 Mar 2023 11:19:29 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 987D325973 for ; Mon, 20 Mar 2023 08:13:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=Xg4UMcVEKxpyYT4k7A+tcw8+E06nhy//K4tdBRqLQdE=; b=O06WPACyqv5mw9P74QLw834z6/ EKunEg1LPuko/rN453nzNgTX2JXlbf2vKL01gusbV9jFSCaJywAQpf0LIhINwuprofRG5glpjnUsa Uza3Uk191eT5pGJ0+jrO5lWn7VGh+cTX9FHYYpzbV6rvTHgRoUWWjz7H9YC22q8wvM7FEPxhmJyHg FKgQg3a40ZFpa/PVTJNW+c30ZSIUZRDQsknutFhoDrI6u7UK8Vd2G+RV5V0xnazpTUsiH3M9qCtGx cKe5BNPC63BW+xmMHjAZHjtxZrG+r5HRCbf2oscnaKjP0mUFJ4ZIJBJXQuYxEuveHL9F8vTG0U7+V f2Pg0kUg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1peHCW-00192K-EJ; Mon, 20 Mar 2023 15:13:32 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 99849300288; Mon, 20 Mar 2023 16:13:31 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7B9D020EEFFC3; Mon, 20 Mar 2023 16:13:31 +0100 (CET) Date: Mon, 20 Mar 2023 16:13:31 +0100 From: Peter Zijlstra To: chi wu Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/core: Reduce cost of sched_move_task when config autogroup Message-ID: <20230320151331.GN2194297@hirez.programming.kicks-ass.net> References: <20230319075643.28312-1-wuchi.zero@gmail.com> <20230320082811.GD2194297@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 20, 2023 at 08:40:51PM +0800, chi wu wrote: > Peter Zijlstra 于2023年3月20日周一 16:28写道： > > > > On Sun, Mar 19, 2023 at 03:56:43PM +0800, wuchi wrote: > > > Some sched_move_task calls of autogroup is useless when the > > > task_struct->sched_task_group isn't changed because of task_group > > > of cpu_cgroup overlay task_group of autogroup. The overlay key codes > > > are as follows: > > > > > > sched_cgroup_fork->autogroup_task_group->task_wants_autogroup > > > sched_change_group->autogroup_task_group->autogroup_task_group > > > > > > sched_move_task eg: > > > task A belongs to cpu_cgroup0 and autogroup0, it will always to > > > cpu_cgroup0 when doing exit. So there is no need to do {de|en}queue. > > > The call graph is as follow. > > > > > > do_exit > > > sched_autogroup_exit_task > > > sched_move_task > > > dequeue_task > > > sched_change_group > > > A.sched_task_group = sched_get_task_group > > > enqueue_task > > > > > > So do some check before dequeue task in sched_move_task. > > > > No immediate objection; but the $subject seems to suggest you did this > > for performance reasons, yet there are no performance results in this > > Changelog. How much does this save under what load? > > cpu:bogomips=4600.00 > kernel:6.3.0-rc3 > cpu cgroup: 6:cpu,cpuacct:/user.slice > > run cmds: > > #!/bin/bash > for i in {0..10000}; do > sleep 0 & > done > wait > > bpftrace -e 'k:sched_move_task { @ts[tid] = nsecs; } > kr:sched_move_task /@ts[tid]/ { @ns += nsecs - @ts[tid]; > delete(@ts[tid]); }' > > cost time(ns): > without patch: 43528033 > with patch: 18934496 > diff: -24593537 -56.5% > > About the change, move sched_task_group_changed before > update_rq_clock as following and add the performance results in > the Changelog? Yes please, that gives good motivation for the change. Thanks!