From nobody Sun Feb 8 21:32:30 2026 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 C709CC6FD1C for ; Wed, 22 Mar 2023 09:23:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230228AbjCVJXM (ORCPT ); Wed, 22 Mar 2023 05:23:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35940 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229550AbjCVJXI (ORCPT ); Wed, 22 Mar 2023 05:23:08 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B49B05DEDE; Wed, 22 Mar 2023 02:22:27 -0700 (PDT) Date: Wed, 22 Mar 2023 09:22:24 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1679476945; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zz9ppyfae31Jdq8hRGy2CPEZ9oMRwUzniy9rsq8qKRs=; b=S5+uMMMrPI+L/wq9RR4FzUpMS4FUAFN5FA3vkbeqe70Cwv61zRsjzu771AUEOD/cQqeTm6 wFyVY9U92PttN37opCb/zwHLBGuBiwJ9n2fopNYk0ik4WzK3bJC4o4l0YhiGXGq7uRrq2R oTQBxzwEFRh/aQAbeIWwrlMsJh9UkOoM2Ce9R0VQVqe2n99vxbNinuGgai5Vj6H3Y2no17 afSFFgqcIgT5cJY6JHU4VDl6mmdf1SPByyyUERZy58DPp7Ft1D6RYUMogx/LCG+krM9ldd 1OBnYkQ6KtWoAAyyllYjJSaemorhaunIj3caVV+8jurCex3KXXMopoE5Brm4ng== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1679476945; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zz9ppyfae31Jdq8hRGy2CPEZ9oMRwUzniy9rsq8qKRs=; b=vykCPShvKvzArN6yIuspDgMWIMOVm7sGHKrhRWINJYH5ksxfzZSyPKwouYezV5kjziJK2A CRRrvll4f+0MHzAQ== From: "tip-bot2 for wuchi" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/core: Reduce cost of sched_move_task when config autogroup Cc: wuchi , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230321064459.39421-1-wuchi.zero@gmail.com> References: <20230321064459.39421-1-wuchi.zero@gmail.com> MIME-Version: 1.0 Message-ID: <167947694474.5837.2005982261299761912.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: eff6c8ce8d4d7faef75f66614dd20bb50595d261 Gitweb: https://git.kernel.org/tip/eff6c8ce8d4d7faef75f66614dd20bb50= 595d261 Author: wuchi AuthorDate: Tue, 21 Mar 2023 14:44:59 +08:00 Committer: Peter Zijlstra CommitterDate: Wed, 22 Mar 2023 10:10:58 +01:00 sched/core: Reduce cost of sched_move_task when config autogroup Some sched_move_task calls are useless because that task_struct->sched_task_group maybe not changed (equals task_group of cpu_cgroup) when system enable autogroup. So do some checks in sched_move_task. sched_move_task eg: task A belongs to cpu_cgroup0 and autogroup0, it will always belong to cpu_cgroup0 when do_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 =3D sched_get_task_group (=3Dcpu_cgroup0) enqueue_task Performance results: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D 1. env cpu: bogomips=3D4600.00 kernel: 6.3.0-rc3 cpu_cgroup: 6:cpu,cpuacct:/user.slice 2. cmds do_exit script: for i in {0..10000}; do sleep 0 & done wait Run the above script, then use the following bpftrace cmd to get the cost of sched_move_task: bpftrace -e 'k:sched_move_task { @ts[tid] =3D nsecs; } kr:sched_move_task /@ts[tid]/ { @ns +=3D nsecs - @ts[tid]; delete(@ts[tid]); }' 3. cost time(ns): without patch: 43528033 with patch: 18541416 diff:-24986617 -57.4% As the result show, the patch will save 57.4% in the scenario. Signed-off-by: wuchi Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230321064459.39421-1-wuchi.zero@gmail.com --- kernel/sched/core.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9140a33..5ddd961 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -10351,7 +10351,7 @@ void sched_release_group(struct task_group *tg) spin_unlock_irqrestore(&task_group_lock, flags); } =20 -static void sched_change_group(struct task_struct *tsk) +static struct task_group *sched_get_task_group(struct task_struct *tsk) { struct task_group *tg; =20 @@ -10363,7 +10363,13 @@ static void sched_change_group(struct task_struct = *tsk) tg =3D container_of(task_css_check(tsk, cpu_cgrp_id, true), struct task_group, css); tg =3D autogroup_task_group(tsk, tg); - tsk->sched_task_group =3D tg; + + return tg; +} + +static void sched_change_group(struct task_struct *tsk, struct task_group = *group) +{ + tsk->sched_task_group =3D group; =20 #ifdef CONFIG_FAIR_GROUP_SCHED if (tsk->sched_class->task_change_group) @@ -10384,10 +10390,19 @@ void sched_move_task(struct task_struct *tsk) { int queued, running, queue_flags =3D DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; + struct task_group *group; struct rq_flags rf; struct rq *rq; =20 rq =3D task_rq_lock(tsk, &rf); + /* + * Esp. with SCHED_AUTOGROUP enabled it is possible to get superfluous + * group changes. + */ + group =3D sched_get_task_group(tsk); + if (group =3D=3D tsk->sched_task_group) + goto unlock; + update_rq_clock(rq); =20 running =3D task_current(rq, tsk); @@ -10398,7 +10413,7 @@ void sched_move_task(struct task_struct *tsk) if (running) put_prev_task(rq, tsk); =20 - sched_change_group(tsk); + sched_change_group(tsk, group); =20 if (queued) enqueue_task(rq, tsk, queue_flags); @@ -10412,6 +10427,7 @@ void sched_move_task(struct task_struct *tsk) resched_curr(rq); } =20 +unlock: task_rq_unlock(rq, tsk, &rf); }