From nobody Wed Dec 17 07:59:18 2025 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 65FF1E732DB for ; Thu, 28 Sep 2023 15:04:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231438AbjI1PEM (ORCPT ); Thu, 28 Sep 2023 11:04:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39348 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231376AbjI1PEK (ORCPT ); Thu, 28 Sep 2023 11:04:10 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71F2D19D for ; Thu, 28 Sep 2023 08:03:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695913400; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=/h6rE6bpiAM9ij7SlW0awDXvs8flnbuUhUxmzCM1x5k=; b=TS/xGxPFXDEA4ldzkFrdnCDtHqFZDhoECEVtlp1pVJqiqwtbGC/A86OmkBqpjSHlGKryD2 oRnbkG+BniJCV4oN2YWvd8ANdRa0aQ8nFH+huXTnYRiy1BxklHIRluQCJEbqaTxziN6Hok KVLTJgAT54sEV0GCGw6iPB3XuqguK8Y= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-616-cWoLB16ENyuVhoeVBH1vPw-1; Thu, 28 Sep 2023 11:03:17 -0400 X-MC-Unique: cWoLB16ENyuVhoeVBH1vPw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2C278101A53B; Thu, 28 Sep 2023 15:03:16 +0000 (UTC) Received: from vschneid.remote.csb (unknown [10.39.193.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1E834C15BB8; Thu, 28 Sep 2023 15:03:13 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: Daniel Bristot de Oliveira , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Peter Zijlstra , Steven Rostedt , Vincent Guittot , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH] sched/deadline: Make dl_rq->pushable_dl_tasks updates drive dl_rq->overloaded Date: Thu, 28 Sep 2023 17:02:51 +0200 Message-Id: <20230928150251.463109-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" dl_nr_migratory is increased whenever a DL entity is enqueued and it has nr_cpus_allowed > 1. Unlike the pushable_dl_tasks tree, dl_nr_migratory includes a dl_rq's current task. This means a dl_rq can have a migratable current, N non-migratable queued tasks, and be flagged as overloaded and ha= ve its CPU set in the dlo_mask, despite having an empty pushable_tasks tree. Make an dl_rq's overload logic be driven by {enqueue,dequeue}_pushable_dl_t= ask(), in other words make DL RQs only be flagged as overloaded if they have at least one runnable-but-not-current migratable task. o push_dl_task() is unaffected, as it is a no-op if there are no pushable tasks. o pull_dl_task() now no longer scans runqueues whose sole migratable task is their current one, which it can't do anything about anyway. It may also now pull tasks to a DL RQ with dl_nr_running > 1 if only its current task is migratable. Since dl_rq->dl_nr_migratory becomes unused, remove it. RT had the exact same mechanism (rt_rq->rt_nr_migratory) which was dropped in favour of relying on rt_rq->pushable_tasks, see: 612f769edd06 ("sched/rt: Make rt_rq->pushable_tasks updates drive rto_mas= k") Link: https://lore.kernel.org/all/20230811112044.3302588-1-vschneid@redhat.= com/ Signed-off-by: Valentin Schneider Acked-by: Juri Lelli Reviewed-by: Daniel Bristot de Oliveira --- kernel/sched/deadline.c | 57 ++++++++++------------------------------- kernel/sched/debug.c | 1 - kernel/sched/sched.h | 1 - 3 files changed, 14 insertions(+), 45 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fb1996a674db5..d98408a274e52 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -509,7 +509,6 @@ void init_dl_rq(struct dl_rq *dl_rq) /* zero means no -deadline tasks */ dl_rq->earliest_dl.curr =3D dl_rq->earliest_dl.next =3D 0; =20 - dl_rq->dl_nr_migratory =3D 0; dl_rq->overloaded =3D 0; dl_rq->pushable_dl_tasks_root =3D RB_ROOT_CACHED; #else @@ -553,39 +552,6 @@ static inline void dl_clear_overload(struct rq *rq) cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask); } =20 -static void update_dl_migration(struct dl_rq *dl_rq) -{ - if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) { - if (!dl_rq->overloaded) { - dl_set_overload(rq_of_dl_rq(dl_rq)); - dl_rq->overloaded =3D 1; - } - } else if (dl_rq->overloaded) { - dl_clear_overload(rq_of_dl_rq(dl_rq)); - dl_rq->overloaded =3D 0; - } -} - -static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *= dl_rq) -{ - struct task_struct *p =3D dl_task_of(dl_se); - - if (p->nr_cpus_allowed > 1) - dl_rq->dl_nr_migratory++; - - update_dl_migration(dl_rq); -} - -static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *= dl_rq) -{ - struct task_struct *p =3D dl_task_of(dl_se); - - if (p->nr_cpus_allowed > 1) - dl_rq->dl_nr_migratory--; - - update_dl_migration(dl_rq); -} - #define __node_2_pdl(node) \ rb_entry((node), struct task_struct, pushable_dl_tasks) =20 @@ -594,6 +560,11 @@ static inline bool __pushable_less(struct rb_node *a, = const struct rb_node *b) return dl_entity_preempt(&__node_2_pdl(a)->dl, &__node_2_pdl(b)->dl); } =20 +static inline int has_pushable_dl_tasks(struct rq *rq) +{ + return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root); +} + /* * The list of pushable -deadline task is not a plist, like in * sched_rt.c, it is an rb-tree with tasks ordered by deadline. @@ -609,6 +580,11 @@ static void enqueue_pushable_dl_task(struct rq *rq, st= ruct task_struct *p) __pushable_less); if (leftmost) rq->dl.earliest_dl.next =3D p->dl.deadline; + + if (!rq->dl.overloaded) { + dl_set_overload(rq); + rq->dl.overloaded =3D 1; + } } =20 static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p) @@ -625,11 +601,11 @@ static void dequeue_pushable_dl_task(struct rq *rq, s= truct task_struct *p) dl_rq->earliest_dl.next =3D __node_2_pdl(leftmost)->dl.deadline; =20 RB_CLEAR_NODE(&p->pushable_dl_tasks); -} =20 -static inline int has_pushable_dl_tasks(struct rq *rq) -{ - return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root); + if (!has_pushable_dl_tasks(rq) && rq->dl.overloaded) { + dl_clear_overload(rq); + rq->dl.overloaded =3D 0; + } } =20 static int push_dl_task(struct rq *rq); @@ -1504,7 +1480,6 @@ void inc_dl_tasks(struct sched_dl_entity *dl_se, stru= ct dl_rq *dl_rq) add_nr_running(rq_of_dl_rq(dl_rq), 1); =20 inc_dl_deadline(dl_rq, deadline); - inc_dl_migration(dl_se, dl_rq); } =20 static inline @@ -1518,7 +1493,6 @@ void dec_dl_tasks(struct sched_dl_entity *dl_se, stru= ct dl_rq *dl_rq) sub_nr_running(rq_of_dl_rq(dl_rq), 1); =20 dec_dl_deadline(dl_rq, dl_se->deadline); - dec_dl_migration(dl_se, dl_rq); } =20 static inline bool __dl_less(struct rb_node *a, const struct rb_node *b) @@ -2291,9 +2265,6 @@ static int push_dl_task(struct rq *rq) struct rq *later_rq; int ret =3D 0; =20 - if (!rq->dl.overloaded) - return 0; - next_task =3D pick_next_pushable_dl_task(rq); if (!next_task) return 0; diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index c4253bd2dfb01..4580a450700ec 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -745,7 +745,6 @@ void print_dl_rq(struct seq_file *m, int cpu, struct dl= _rq *dl_rq) =20 PU(dl_nr_running); #ifdef CONFIG_SMP - PU(dl_nr_migratory); dl_bw =3D &cpu_rq(cpu)->rd->dl_bw; #else dl_bw =3D &dl_rq->dl_bw; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 41d760df458f7..649eb9ec06575 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -707,7 +707,6 @@ struct dl_rq { u64 next; } earliest_dl; =20 - unsigned int dl_nr_migratory; int overloaded; =20 /* --=20 2.31.1