From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6684C433E0 for ; Fri, 7 Aug 2020 09:51:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B46B82177B for ; Fri, 7 Aug 2020 09:51:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ccII5+/Z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728300AbgHGJvg (ORCPT ); Fri, 7 Aug 2020 05:51:36 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:46125 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727820AbgHGJvf (ORCPT ); Fri, 7 Aug 2020 05:51:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596793892; 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: in-reply-to:in-reply-to:references:references; bh=Z8tgJTs+X+8vEZKUl5jq8+JAws3cxDj6P8K3XwwrUrQ=; b=ccII5+/Za3BwGxsRqqUMJVeGj8lLrijfSF9+VgxgsRGyQRaDZkotKa6pB9GwgnqoXLb6/A 3LNgTAAo0HVC5UXOONvy0otPaNEdRJbCTSll89aVixeeyyvb8D2geVliXSc6Zn2rmccAuM h//O5c28n1C49arfmBLiOJ06aFlY7qI= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-438-C29s-3rNOPCiTuVjJ9zamA-1; Fri, 07 Aug 2020 05:51:31 -0400 X-MC-Unique: C29s-3rNOPCiTuVjJ9zamA-1 Received: by mail-wr1-f71.google.com with SMTP id b13so535322wrq.19 for ; Fri, 07 Aug 2020 02:51:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Z8tgJTs+X+8vEZKUl5jq8+JAws3cxDj6P8K3XwwrUrQ=; b=bXDjtq5E+Hfs2QY5gV5HKYr5OZ3bIM6oZL+c6M/xkbzFy6U0mBxkEu57RBaNvTqeDQ n/lgT+Kh/4NlEhDjdgaDiF4t3nZdofLkhGc2DxihBqbhREQU2UeFLMx5d6Wq9U1/N0WV zAjYkGT9nomMpNsliWHFYEnIKwjHprxaK0M1FhUTYQzGbNdjBJpEuV0YdalPvV6tbXTv 8SjaNeBe3TkfrU1kB21L2DQmsEg63ArVelQwCUF99GcOsUjzqtDWzC4rG52raEbXwbFA mP2QCZ0VOF1C3E2E3kuV0GKHUuOZJ8ZvEb6B6KxEwmd+b4TjPj0gMJ2hD4C5VgKuIWfP RIcg== X-Gm-Message-State: AOAM532HbDIFD53VoML8RYp2AEygxQeMKRgdoMD9WH8igP/Q65f7lIfL bOhEvZnnNmLczPsv1vXTVy3WxY9VQpByLS+WxBWwWYzzlcoiHvmU+bMa0mY5tft42UBJXABSVFG xuXtoWURqG0FcbajXEYujvqmMmNI= X-Received: by 2002:a05:6000:12c1:: with SMTP id l1mr10782164wrx.270.1596793888628; Fri, 07 Aug 2020 02:51:28 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzoF/IgfG/wrZaT1KmhKuf9rOoHeqn6nVwIPqkddHT7tcqpp9p7N0WOqR+WS+JPz4qdSbwJ7A== X-Received: by 2002:a05:6000:12c1:: with SMTP id l1mr10782157wrx.270.1596793888413; Fri, 07 Aug 2020 02:51:28 -0700 (PDT) Received: from localhost.localdomain.com ([151.29.36.84]) by smtp.gmail.com with ESMTPSA id h14sm9388396wml.30.2020.08.07.02.51.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Aug 2020 02:51:27 -0700 (PDT) From: Juri Lelli To: peterz@infradead.org, mingo@redhat.com Cc: rostedt@goodmis.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, tommaso.cucinotta@santannapisa.it, alessio.balsini@gmail.com, bristot@redhat.com, dietmar.eggemann@arm.com, linux-rt-users@vger.kernel.org, mtosatti@redhat.com, williams@redhat.com, valentin.schneider@arm.com Subject: [RFC PATCH v2 5/6] sched/fair: Add trivial fair server Date: Fri, 7 Aug 2020 11:50:50 +0200 Message-Id: <20200807095051.385985-6-juri.lelli@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200807095051.385985-1-juri.lelli@redhat.com> References: <20200807095051.385985-1-juri.lelli@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org From: Peter Zijlstra Use deadline servers to service fair tasks. This patch adds a fair_server deadline entity which acts as a container for fair entities and can be used to fix starvation when higher priority (wrt fair) tasks are monopolizing CPU(s). Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/core.c | 1 + kernel/sched/fair.c | 29 +++++++++++++++++++++++++++++ kernel/sched/sched.h | 4 ++++ 3 files changed, 34 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7c471961fd0b8..6537637139c63 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7170,6 +7170,7 @@ void __init sched_init(void) #endif /* CONFIG_SMP */ hrtick_rq_init(rq); atomic_set(&rq->nr_iowait, 0); + fair_server_init(rq); } set_load_weight(&init_task, false); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5130239c0e1e5..6a97ee2a4e26d 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5514,6 +5514,9 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) */ util_est_enqueue(&rq->cfs, p); + if (!rq->cfs.h_nr_running) + dl_server_start(&rq->fair_server); + /* * If in_iowait is set, the code below may not trigger any cpufreq * utilization updates, so do it here explicitly with the IOWAIT flag @@ -5666,6 +5669,9 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) rq->next_balance = jiffies; dequeue_throttle: + if (!rq->cfs.h_nr_running) + dl_server_stop(&rq->fair_server); + util_est_dequeue(&rq->cfs, p, task_sleep); hrtick_update(rq); } @@ -7151,6 +7157,29 @@ static struct task_struct *__pick_next_task_fair(struct rq *rq) return pick_next_task_fair(rq, NULL, NULL); } +static bool fair_server_has_tasks(struct sched_dl_entity *dl_se) +{ + return !!dl_se->rq->cfs.nr_running; +} + +static struct task_struct *fair_server_pick(struct sched_dl_entity *dl_se) +{ + return pick_next_task_fair(dl_se->rq, NULL, NULL); +} + +void fair_server_init(struct rq *rq) +{ + struct sched_dl_entity *dl_se = &rq->fair_server; + + init_dl_entity(dl_se); + + dl_se->dl_runtime = TICK_NSEC; + dl_se->dl_deadline = 20 * TICK_NSEC; + dl_se->dl_period = 20 * TICK_NSEC; + + dl_server_init(dl_se, rq, fair_server_has_tasks, fair_server_pick); +} + /* * Account for a descheduled task: */ diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index f035cd8ccd224..bf8c9c07705c9 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -375,6 +375,8 @@ extern void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq, dl_server_has_tasks_f has_tasks, dl_server_pick_f pick); +extern void fair_server_init(struct rq *); + #ifdef CONFIG_CGROUP_SCHED #include @@ -959,6 +961,8 @@ struct rq { struct rt_rq rt; struct dl_rq dl; + struct sched_dl_entity fair_server; + #ifdef CONFIG_FAIR_GROUP_SCHED /* list of leaf cfs_rq on this CPU: */ struct list_head leaf_cfs_rq_list; -- 2.26.2