From nobody Sat Feb 7 08:02:07 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 E7625C77B73 for ; Wed, 31 May 2023 12:49:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236082AbjEaMtb (ORCPT ); Wed, 31 May 2023 08:49:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235988AbjEaMs7 (ORCPT ); Wed, 31 May 2023 08:48:59 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E0BBE48 for ; Wed, 31 May 2023 05:48:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=tv6sCKoE79EpD05Hd2YDu+LAbWtn1Gj3QHTavbmMia4=; b=EReReZwapFqWEFIy7DpROKSIH9 q1jJLDzgpDvkhe1XTxxvXBhQAoPtKBjTYzafnLkXptHn9yqT3StYSxUJGwGMih3QA2JfnKLgl/UPh U2P3Tc2Qp/0IMoj9cMCowiKz2IbB3cowRjpzGyozNaGheTUHkPWB99Ie6m3WH4SKAojBrdhhbRGGN WGMtY5Ao/JhLv7PN4EKTg9fhdp/2/XjPvjzG3RMiTqETbI6HD9o3tqqyuI+XH7LQ5Z9bLgkX+9q6i 0KOdr9JR01Nz5IS2nFjXPxv3J6A0AaQ/E+D91T8OBCtruT6ZVsln4kpjwN+ZUyqbJov1fGX8Uu+wO feaq7k6w==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1q4LEp-007GRc-WB; Wed, 31 May 2023 12:47:40 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 8CFCB300E25; Wed, 31 May 2023 14:47:37 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 1486922BA645E; Wed, 31 May 2023 14:47:34 +0200 (CEST) Message-ID: <20230531124604.341527144@infradead.org> User-Agent: quilt/0.66 Date: Wed, 31 May 2023 13:58:50 +0200 From: Peter Zijlstra To: mingo@kernel.org, vincent.guittot@linaro.org Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, corbet@lwn.net, qyousef@layalina.io, chris.hyser@oracle.com, patrick.bellasi@matbug.net, pjt@google.com, pavel@ucw.cz, qperret@google.com, tim.c.chen@linux.intel.com, joshdon@google.com, timj@gnu.org, kprateek.nayak@amd.com, yu.c.chen@intel.com, youssefesmat@chromium.org, joel@joelfernandes.org, efault@gmx.de, tglx@linutronix.de Subject: [PATCH 11/15] sched/eevdf: Better handle mixed slice length References: <20230531115839.089944915@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In the case where (due to latency-nice) there are different request sizes in the tree, the smaller requests tend to be dominated by the larger. Also note how the EEVDF lag limits are based on r_max. Therefore; add a heuristic that for the mixed request size case, moves smaller requests to placement strategy #2 which ensures they're immidiately eligible and and due to their smaller (virtual) deadline will cause preemption. NOTE: this relies on update_entity_lag() to impose lag limits above a single slice. Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/fair.c | 30 ++++++++++++++++++++++++++++++ kernel/sched/features.h | 1 + kernel/sched/sched.h | 1 + 3 files changed, 32 insertions(+) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -642,6 +642,7 @@ avg_vruntime_add(struct cfs_rq *cfs_rq, s64 key =3D entity_key(cfs_rq, se); =20 cfs_rq->avg_vruntime +=3D key * weight; + cfs_rq->avg_slice +=3D se->slice * weight; cfs_rq->avg_load +=3D weight; } =20 @@ -652,6 +653,7 @@ avg_vruntime_sub(struct cfs_rq *cfs_rq, s64 key =3D entity_key(cfs_rq, se); =20 cfs_rq->avg_vruntime -=3D key * weight; + cfs_rq->avg_slice -=3D se->slice * weight; cfs_rq->avg_load -=3D weight; } =20 @@ -4908,6 +4910,21 @@ static inline void update_misfit_status( =20 #endif /* CONFIG_SMP */ =20 +static inline bool +entity_has_slept(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) +{ + u64 now; + + if (!(flags & ENQUEUE_WAKEUP)) + return false; + + if (flags & ENQUEUE_MIGRATED) + return true; + + now =3D rq_clock_task(rq_of(cfs_rq)); + return (s64)(se->exec_start - now) >=3D se->slice; +} + static void place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { @@ -4930,6 +4947,19 @@ place_entity(struct cfs_rq *cfs_rq, stru lag =3D se->vlag; =20 /* + * For latency sensitive tasks; those that have a shorter than + * average slice and do not fully consume the slice, transition + * to EEVDF placement strategy #2. + */ + if (sched_feat(PLACE_FUDGE) && + (cfs_rq->avg_slice > se->slice * cfs_rq->avg_load) && + entity_has_slept(cfs_rq, se, flags)) { + lag +=3D vslice; + if (lag > 0) + lag =3D 0; + } + + /* * If we want to place a task and preserve lag, we have to * consider the effect of the new entity on the weighted * average and compensate for this, otherwise lag can quickly --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -5,6 +5,7 @@ * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled. */ SCHED_FEAT(PLACE_LAG, true) +SCHED_FEAT(PLACE_FUDGE, true) SCHED_FEAT(PLACE_DEADLINE_INITIAL, true) =20 /* --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -555,6 +555,7 @@ struct cfs_rq { unsigned int idle_h_nr_running; /* SCHED_IDLE */ =20 s64 avg_vruntime; + u64 avg_slice; u64 avg_load; =20 u64 exec_clock;