From nobody Sun Apr 19 17:04:32 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 6136EC433EF for ; Wed, 29 Jun 2022 01:58:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230099AbiF2B64 (ORCPT ); Tue, 28 Jun 2022 21:58:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229511AbiF2B6y (ORCPT ); Tue, 28 Jun 2022 21:58:54 -0400 Received: from mail-pf1-x436.google.com (mail-pf1-x436.google.com [IPv6:2607:f8b0:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B9B21F607 for ; Tue, 28 Jun 2022 18:58:50 -0700 (PDT) Received: by mail-pf1-x436.google.com with SMTP id t21so13686229pfq.1 for ; Tue, 28 Jun 2022 18:58:50 -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=l2cjPj2rGQYi4IE2tVl3hOTOPJB5V96R0meZ4b9cHtY=; b=q6v56ze5/ph7rfOuScMbsXs4S2SoZHwR7bh2WYvbZEC4a3gm1agQiwIpGjf3UbOhPc CMMDKc/wAnSRbVye633p7+ZrOK1RknUTdV28iRiWMV/xNnkWdhGF6nwT2W9Y3zN3VM39 37meV/f0e4GbWWKqX4DayXOQaUhFWRDExPb/3nnxnJfDBAIXCdupnouyl2bsUCCqjegV ASZPZQQaUmAp0NQMZgwe8z+NgcAPeL6Be/Dv8FMtSSUCcLDPkcS87IZF7HUFn2oHR9pb RmEDmmerhjfj7ozsMLHwc3y1QTT450m9iHt+W76pvdWEVbuIhPT0kp1Agd71pmGbC0vm Oyfg== 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=l2cjPj2rGQYi4IE2tVl3hOTOPJB5V96R0meZ4b9cHtY=; b=2b/eEnqPn3Lhy+e5m19nz3i9VFWNaCVLitRylDa+/10ADQkIZNRvCEZU2eh42/UvDw p8cMdS92dsRQUK3wqysaTQdKVaUPVnKcC9Tt33v7EmtNlIRisSAsDoRmnl9Sd7BF3P6G WCRecOxFv5v3OJdr2mEZNlcXcWXB9N9id+KHs/e/TaJTPHKZ2kdAXLhPUyVlGa+635uX 0pB2/IasGEqdrkVucrZYsO/+C4fo/gBRYG/nQ+iLat7hkXcrAFhVVDKOjUmYpjgormJ+ JqcHe30eUbk2dMsa2sBCxcVfFSYU1G+AhD6EfGDe+1CbXwIDqXODfC7+2yfRF0ZzuNnj C1kw== X-Gm-Message-State: AJIora/UL3m+6aqTaFTBXHbVvMThEFRcPbIYIy7AmYRDiy3497KgpPK6 k0wO6ZyZqhWHh86n3Rws1dwAKw== X-Google-Smtp-Source: AGRyM1vMw39HmKM14XX+Qo7MOVdGShw02oI13NchFH/A/DNJlm+gFcsXirL/oKAKqzvzQUfrAIWcdA== X-Received: by 2002:a63:f24d:0:b0:40d:ed5f:1729 with SMTP id d13-20020a63f24d000000b0040ded5f1729mr861219pgk.338.1656467929749; Tue, 28 Jun 2022 18:58:49 -0700 (PDT) Received: from C02CV1DAMD6P.bytedance.net ([139.177.225.230]) by smtp.gmail.com with ESMTPSA id f5-20020aa79d85000000b005187431876fsm10135114pfq.180.2022.06.28.18.58.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jun 2022 18:58:49 -0700 (PDT) From: Chengming Zhou To: mingo@redhat.com, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com Cc: linux-kernel@vger.kernel.org, Chengming Zhou Subject: [PATCH v5] sched/fair: combine detach into dequeue when migrating task Date: Wed, 29 Jun 2022 09:58:34 +0800 Message-Id: <20220629015834.98407-1-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() 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. detach_task() deactivate_task() dequeue_task_fair() for_each_sched_entity(se) dequeue_entity() update_load_avg() /* (1) */ detach_entity_load_avg() set_task_cpu() migrate_task_rq_fair() detach_entity_cfs_rq() /* (2) */ update_load_avg(); detach_entity_load_avg(); propagate_entity_cfs_rq(); for_each_sched_entity() update_load_avg() This patch save the detach_entity_cfs_rq() called in (2) by doing the detach_entity_load_avg() for a CPU migrating task inside (1) (the task being the first se in the loop) Reviewed-by: Vincent Guittot Signed-off-by: Chengming Zhou --- v5: - improve the commit message suggested by Vincent. 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