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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 AA0C0C433ED for ; Wed, 12 May 2021 10:29:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 782B9613F3 for ; Wed, 12 May 2021 10:29:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230329AbhELKaK (ORCPT ); Wed, 12 May 2021 06:30:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36126 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230357AbhELK3e (ORCPT ); Wed, 12 May 2021 06:29:34 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D1FBC06174A; Wed, 12 May 2021 03:28:26 -0700 (PDT) Date: Wed, 12 May 2021 10:28:23 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1620815304; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=teDgoqbbyHPBFSFxf5VmvnJDjavswgCwPqLiKnvqnNk=; b=jZIefxli097OnCxZCPJ+ntIWVZrkDsSABEomBpnBklcl+/7tSF9fytaAFOcY6IEWWGcXD+ gR56gUqMBkAiEO8WXazysOOiGl1j4LwHtSm+scqL4lgY5NHH3zw8q98NEc7ygeIoq1ZhQa 17x6wRhhz593jG2Is9cL6j2k5amlGMJ4t5shMZqGcUUB4H/BG+xB4FyGWRvKWQ2a6v1QLD cVBWGjYk7HjVCKmiJaxSEcawpr1LW+4EzobTzi988u8ZKaswxY8v2EEyC23PWvhZLUhleo DspMEyImOWf29AlHwz1YeZ9cVma6bFGoNmmMAgRHgzMAZvQs9kktnpy0O86SRg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1620815304; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=teDgoqbbyHPBFSFxf5VmvnJDjavswgCwPqLiKnvqnNk=; b=YDUSTIcx/ntGW4pJ6iOWhqtxm3XRBzTzDDrFITSz9SyorqYUWK/42qcL9pzqb/PTPENzdD qdojEovpjZ5oowDg== From: "tip-bot2 for Vineeth Pillai" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/fair: Fix forced idle sibling starvation corner case Cc: Vineeth Pillai , "Peter Zijlstra (Intel)" , Don Hiatt , Hongyu Ning , Vincent Guittot , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210422123308.617407840@infradead.org> References: <20210422123308.617407840@infradead.org> MIME-Version: 1.0 Message-ID: <162081530396.29796.6078425028359112311.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 8039e96fcc1de30d5bcaf05da9ca2de46a800826 Gitweb: https://git.kernel.org/tip/8039e96fcc1de30d5bcaf05da9ca2de46a800826 Author: Vineeth Pillai AuthorDate: Tue, 17 Nov 2020 18:19:38 -05:00 Committer: Peter Zijlstra CommitterDate: Wed, 12 May 2021 11:43:29 +02:00 sched/fair: Fix forced idle sibling starvation corner case If there is only one long running local task and the sibling is forced idle, it might not get a chance to run until a schedule event happens on any cpu in the core. So we check for this condition during a tick to see if a sibling is starved and then give it a chance to schedule. Signed-off-by: Vineeth Pillai Signed-off-by: Peter Zijlstra (Intel) Tested-by: Don Hiatt Tested-by: Hongyu Ning Tested-by: Vincent Guittot Link: https://lkml.kernel.org/r/20210422123308.617407840@infradead.org --- kernel/sched/core.c | 15 ++++++++------- kernel/sched/fair.c | 40 ++++++++++++++++++++++++++++++++++++++++ kernel/sched/sched.h | 2 +- 3 files changed, 49 insertions(+), 8 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index db763f4..f5e1e6f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5459,16 +5459,15 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) /* reset state */ rq->core->core_cookie = 0UL; + if (rq->core->core_forceidle) { + need_sync = true; + rq->core->core_forceidle = false; + } for_each_cpu(i, smt_mask) { struct rq *rq_i = cpu_rq(i); rq_i->core_pick = NULL; - if (rq_i->core_forceidle) { - need_sync = true; - rq_i->core_forceidle = false; - } - if (i != cpu) update_rq_clock(rq_i); } @@ -5588,8 +5587,10 @@ next_class:; if (!rq_i->core_pick) continue; - if (is_task_rq_idle(rq_i->core_pick) && rq_i->nr_running) - rq_i->core_forceidle = true; + if (is_task_rq_idle(rq_i->core_pick) && rq_i->nr_running && + !rq_i->core->core_forceidle) { + rq_i->core->core_forceidle = true; + } if (i == cpu) { rq_i->core_pick = NULL; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 08be7a2..4d1ecab 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10767,6 +10767,44 @@ static void rq_offline_fair(struct rq *rq) #endif /* CONFIG_SMP */ +#ifdef CONFIG_SCHED_CORE +static inline bool +__entity_slice_used(struct sched_entity *se, int min_nr_tasks) +{ + u64 slice = sched_slice(cfs_rq_of(se), se); + u64 rtime = se->sum_exec_runtime - se->prev_sum_exec_runtime; + + return (rtime * min_nr_tasks > slice); +} + +#define MIN_NR_TASKS_DURING_FORCEIDLE 2 +static inline void task_tick_core(struct rq *rq, struct task_struct *curr) +{ + if (!sched_core_enabled(rq)) + return; + + /* + * If runqueue has only one task which used up its slice and + * if the sibling is forced idle, then trigger schedule to + * give forced idle task a chance. + * + * sched_slice() considers only this active rq and it gets the + * whole slice. But during force idle, we have siblings acting + * like a single runqueue and hence we need to consider runnable + * tasks on this cpu and the forced idle cpu. Ideally, we should + * go through the forced idle rq, but that would be a perf hit. + * We can assume that the forced idle cpu has atleast + * MIN_NR_TASKS_DURING_FORCEIDLE - 1 tasks and use that to check + * if we need to give up the cpu. + */ + if (rq->core->core_forceidle && rq->cfs.nr_running == 1 && + __entity_slice_used(&curr->se, MIN_NR_TASKS_DURING_FORCEIDLE)) + resched_curr(rq); +} +#else +static inline void task_tick_core(struct rq *rq, struct task_struct *curr) {} +#endif + /* * scheduler tick hitting a task of our scheduling class. * @@ -10790,6 +10828,8 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) update_misfit_status(curr, rq); update_overutilized_status(task_rq(curr)); + + task_tick_core(rq, curr); } /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index dd44a31..db55514 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1083,12 +1083,12 @@ struct rq { unsigned int core_enabled; unsigned int core_sched_seq; struct rb_root core_tree; - unsigned char core_forceidle; /* shared state */ unsigned int core_task_seq; unsigned int core_pick_seq; unsigned long core_cookie; + unsigned char core_forceidle; #endif };