From nobody Sun Apr 26 08:21:19 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 EDB84C43334 for ; Mon, 20 Jun 2022 14:21:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243188AbiFTOVv (ORCPT ); Mon, 20 Jun 2022 10:21:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244097AbiFTOV0 (ORCPT ); Mon, 20 Jun 2022 10:21:26 -0400 Received: from mail-pj1-x1032.google.com (mail-pj1-x1032.google.com [IPv6:2607:f8b0:4864:20::1032]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EF00147558 for ; Mon, 20 Jun 2022 06:36:16 -0700 (PDT) Received: by mail-pj1-x1032.google.com with SMTP id h9-20020a17090a648900b001ecb8596e43so1146743pjj.5 for ; Mon, 20 Jun 2022 06:36:16 -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=eCAoe29EBiPTzk/vFzOmNSRY5Vl8DK3KBtOJG6UlV8E=; b=Pg5a7m6s0vjD/nJh3llC1zxSPB8Xv6mHgQSbWFb8ZK/WRfgNwo7nQPiMGrTwZZuIKc kPHkRdg/v9ZCJbqJz3Ga8/RakxCTpPITohVH4b0cJCx29lQNmAJyFHttNjOLIaZhhRtV WhVmD5rHbiN0K6anskQRr/lNDt8uWyex+/y2d9CqIlsfaXNhsY2SiOLKKRbZwCtblRgu 1gBfZ0RmARgpSpeoLiyRR2/6YIkMkO8eJcr/mEYln5tIlr8WOly6kYRgJtbkxd3aRxEt y1b7/pS4JKI01EEGPmmYFYiJVHrKVosvu94bhwWvIiOh2FmvYqteGEkn0hMjjIDo2foZ ii2A== 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=eCAoe29EBiPTzk/vFzOmNSRY5Vl8DK3KBtOJG6UlV8E=; b=n/YrnQ6E1hVdyy7SUklIJ0nBNLQ8bMm73qdnKTLV9syq23JCztBjstrAae7wIsV1UE bptyVcZb+MmX2NnuEdpT4BPnMBsLh7CcbPHRu7dMbEMTX1sUft6K+pypdeVT1Az6p4fa AbvdqMK5r8PqugAg6YyLFwS2tFKzX9V/gSXrNRFAkZWebV+yF7Gen0a/o3D2pGd9pmWG 7kyDqVhkhX7I35pDjeLQYp84594JOD+VBw/XL0+IuECW+KtrxJHrR0ZqDrKtnsj02Uas jbgEuG+PHU7JLy/00RccF5v3jkRBs9XYq80q0roj3Ji+GVHvo87aA8xJPkxx1Xe6oBYu yqUQ== X-Gm-Message-State: AJIora/r3gQTN6jHG+RTHdnyrl1E+AKhr9ShpoqrcpnBeooSbNiA7xTl o26EtS3bKzuIUGoYPw8Q0Q+iVg== X-Google-Smtp-Source: AGRyM1v8ZRd50pfl7nEp+lJ0xPCuaLT2ShZFVp7wPmDSba5Evq+z3TUkj1HA3zSf/BK3RLaB2KybZg== X-Received: by 2002:a17:902:eccf:b0:168:faa0:4eed with SMTP id a15-20020a170902eccf00b00168faa04eedmr23623736plh.139.1655732175685; Mon, 20 Jun 2022 06:36:15 -0700 (PDT) Received: from C02CV1DAMD6P.bytedance.net ([139.177.225.233]) by smtp.gmail.com with ESMTPSA id c11-20020aa7952b000000b0052521fd273fsm2363893pfp.218.2022.06.20.06.36.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jun 2022 06:36:15 -0700 (PDT) From: Chengming Zhou To: mingo@redhat.com, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, vschneid@redhat.com Cc: linux-kernel@vger.kernel.org, Chengming Zhou Subject: [PATCH v4] sched/fair: combine detach into dequeue when migrating task Date: Mon, 20 Jun 2022 21:36:08 +0800 Message-Id: <20220620133608.78498-1-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 and propagation into dequeue_entity() to save the detach_entity_cfs_rq() -> propagate_entity_cfs_rq() call in 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 extra time to do the detach_entity_cfs_rq() -> propagate_entity_cfs_rq() call, which wouldn't be called anymore with this patch's change. Copied from Dietmar's much clearer comment: 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 Reviewed-by: Vincent Guittot --- v4: - change the commit message a little. - remove the forward declaration of detach_entity_cfs_rq() - remove verbose comments in code. 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 | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8bed75757e65..31d53c11e244 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3931,6 +3931,7 @@ 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) @@ -3948,7 +3949,14 @@ 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(). @@ -4241,6 +4249,7 @@ 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) { @@ -4460,6 +4469,11 @@ 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 (entity_is_task(se) && task_on_rq_migrating(task_of(se))) + action |=3D DO_DETACH; + /* * Update run-time statistics of the 'current'. */ @@ -4473,7 +4487,7 @@ 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); @@ -6938,8 +6952,6 @@ select_task_rq_fair(struct task_struct *p, int prev_c= pu, int wake_flags) return new_cpu; } =20 -static void detach_entity_cfs_rq(struct sched_entity *se); - /* * Called immediately before a task is migrated to a new CPU; task_cpu(p) = and * cfs_rq_of(p) references at time of call are still valid and identify the @@ -6973,15 +6985,7 @@ 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 { + 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