From nobody Mon Apr 27 19:15:55 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 E94B8C43334 for ; Fri, 10 Jun 2022 11:13:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243227AbiFJLNm (ORCPT ); Fri, 10 Jun 2022 07:13:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344921AbiFJLNk (ORCPT ); Fri, 10 Jun 2022 07:13:40 -0400 Received: from mail-pf1-x42b.google.com (mail-pf1-x42b.google.com [IPv6:2607:f8b0:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80ACB6348 for ; Fri, 10 Jun 2022 04:13:36 -0700 (PDT) Received: by mail-pf1-x42b.google.com with SMTP id x4so15021410pfj.10 for ; Fri, 10 Jun 2022 04:13:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=LVa3XUxgHKX1MSYbB7p045eDLlQ/+b7ejFaAsKdJpTI=; b=74AR0ovxnSvd6fosuLJuwY3kqMZo9hWdh1O4YoRW1DEWfeXFDHHOvXoEm2aVzE9VjY RgPYUU/X/Dz+4Jhpack8ClrtgEUEWfaZyb90s2HhlYgJLrTySaz81e+ga3cCI3imWVhV lOeuDfnr3TocYUOK4C2SH7ipMTFqgay1yPEwKCcCPZudz9HJBD9lJtiOqjDvA8iyN/6L CXHgbJkQId1SHrQPn2/kDaH54o1vXu0caRLgGWq4/ogMoNW6tDdpbEw9ns9G/o4PopIn a1ADbAgJQ3kTZ2o3cl/9Sa8sClks5qtoJm4iZXxh7HdvOoHajsSOuHNhXlrBTyCOPbdh N2NQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=LVa3XUxgHKX1MSYbB7p045eDLlQ/+b7ejFaAsKdJpTI=; b=BQuzfprryAkSVVUV2lsiuGEEMQDJh5bFYSTFKVsM3JXGunnftyIixPhDwgbRw1ecJm nJ7Xmukw7Px2dOI3svJIVWyHpnr8nccwaMXm8CEZUbgVCFs4PiYe+2MLc2iNMjjO0Ys7 apD1bjz8uBLiTMIEbiQck86NrSYF9sFIbraZwtVz1o5sAVyFVOyQCPgJqiNEJupIQP9Q ucqD8TgqC6cSWWs8uRYPsOKsWAoDipclwOGlzj9oOmwg3Bg64C+zDOnT050VqhdygI9L 1rLzqVDkAU+l0lnVoUmDdGIKHhL5hqvIaAdHEBiaMuJQp//cZYpsCvxjgSPY1SMoNfOh oh7Q== X-Gm-Message-State: AOAM531uuTJwkyAW4Wu/1p987wQxJX2ug/5NEPRAZmxDs4wUyohcqQeT fOee6VVXIaeoj4JMXvHpEiZaXw== X-Google-Smtp-Source: ABdhPJxez3dVgnFFd0Ik5qQAg2OYJnHt4X42odo1jVXM0qHZ5s0lzGsHPZgMW932by+VVOKRzqM5VQ== X-Received: by 2002:a63:6cb:0:b0:403:af21:972e with SMTP id 194-20020a6306cb000000b00403af21972emr2140137pgg.90.1654859616039; Fri, 10 Jun 2022 04:13:36 -0700 (PDT) Received: from C02CV1DAMD6P.bytedance.net ([139.177.225.248]) by smtp.gmail.com with ESMTPSA id g126-20020a625284000000b0050dc76281e0sm19190862pfb.186.2022.06.10.04.13.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jun 2022 04:13:35 -0700 (PDT) From: Chengming Zhou To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de Cc: linux-kernel@vger.kernel.org, duanxiongchun@bytedance.com, songmuchun@bytedance.com, Chengming Zhou Subject: [PATCH v3] sched/fair: combine detach into dequeue when migrating task Date: Fri, 10 Jun 2022 19:13:27 +0800 Message-Id: <20220610111327.47925-1-zhouchengming@bytedance.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When we are migrating task out of the CPU, we can combine detach into dequeue_entity() to save the independent detach_entity_cfs_rq() in migrate_task_rq_fair(). This optimization is like combining DO_ATTACH in the enqueue_entity() when migrating task to the CPU. So we don't have to traverse the CFS tree twice to do the detach_entity_cfs_rq() -> propagate_entity_cfs_rq() call, this one wouldn't be called anymore with this patch's change. detach_task() deactivate_task() dequeue_task_fair() for_each_sched_entity(se) dequeue_entity() update_load_avg() /* (1) */ set_task_cpu() migrate_task_rq_fair() /* called detach_entity_cfs_rq() before the patch (2) */ This patch save the propagate_entity_cfs_rq(&p->se) call from (2) by doing the detach_entity_load_avg(), update_tg_load_avg() for a migrating task inside (1) (the task being the first se in the loop) Signed-off-by: Chengming Zhou --- v3: - change to use task_on_rq_migrating() and put Dietmar's much clearer description in the commit message. Thanks! v2: - fix !CONFIG_SMP build error --- kernel/sched/fair.c | 34 +++++++++++++++++++++++----------- 1 file changed, 23 insertions(+), 11 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e0cd4052e32f..db85c3c2415a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3896,6 +3896,7 @@ static void detach_entity_load_avg(struct cfs_rq *cfs= _rq, struct sched_entity *s #define UPDATE_TG 0x1 #define SKIP_AGE_LOAD 0x2 #define DO_ATTACH 0x4 +#define DO_DETACH 0x8 =20 /* Update task and its cfs_rq load average */ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_ent= ity *se, int flags) @@ -3913,7 +3914,14 @@ static inline void update_load_avg(struct cfs_rq *cf= s_rq, struct sched_entity *s decayed =3D update_cfs_rq_load_avg(now, cfs_rq); decayed |=3D propagate_entity_load_avg(se); =20 - if (!se->avg.last_update_time && (flags & DO_ATTACH)) { + if (flags & DO_DETACH) { + /* + * DO_DETACH means we're here from dequeue_entity() + * and we are migrating task out of the CPU. + */ + detach_entity_load_avg(cfs_rq, se); + update_tg_load_avg(cfs_rq); + } else if (!se->avg.last_update_time && (flags & DO_ATTACH)) { =20 /* * DO_ATTACH means we're here from enqueue_entity(). @@ -4206,6 +4214,7 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *c= fs_rq) #define UPDATE_TG 0x0 #define SKIP_AGE_LOAD 0x0 #define DO_ATTACH 0x0 +#define DO_DETACH 0x0 =20 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_ent= ity *se, int not_used1) { @@ -4426,6 +4435,14 @@ static __always_inline void return_cfs_rq_runtime(st= ruct cfs_rq *cfs_rq); static void dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { + int action =3D UPDATE_TG; + + /* + * If we are migrating task from the CPU, detach load_avg when dequeue. + */ + if (entity_is_task(se) && task_on_rq_migrating(task_of(se))) + action |=3D DO_DETACH; + /* * Update run-time statistics of the 'current'. */ @@ -4440,7 +4457,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_en= tity *se, int flags) * - For group entity, update its weight to reflect the new share * of its group cfs_rq. */ - update_load_avg(cfs_rq, se, UPDATE_TG); + update_load_avg(cfs_rq, se, action); se_update_runnable(se); =20 update_stats_dequeue_fair(cfs_rq, se, flags); @@ -6940,15 +6957,10 @@ static void migrate_task_rq_fair(struct task_struct= *p, int new_cpu) se->vruntime -=3D min_vruntime; } =20 - if (p->on_rq =3D=3D TASK_ON_RQ_MIGRATING) { - /* - * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old' - * rq->lock and can modify state directly. - */ - lockdep_assert_rq_held(task_rq(p)); - detach_entity_cfs_rq(&p->se); - - } else { + /* + * In case of TASK_ON_RQ_MIGRATING we already detach in dequeue_entity. + */ + if (!task_on_rq_migrating(p)) { /* * We are supposed to update the task to "current" time, then * its up to date and ready to go to new CPU/cfs_rq. But we --=20 2.36.1