From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8F4FF3A6403; Wed, 13 May 2026 11:35:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778672141; cv=none; b=JXYHYy3fEq464hDadPun7NcpKe0U2phmqyY9HBUyl+X5IEfXZanuKtEh+m6KfDb1zD8TbBhMu+NfcMAcDfIuxjSs7n48QT/a2SQvpBRjMObJvN3UNrRa5bGVIHESfv1XGGWEDAL4oknuiqIn8hMtfPMmC5UGZzXVei4DY3wG68g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778672141; c=relaxed/simple; bh=wYfaGw3jnHUOhqZLBYPdMUGhcpYlXQqdttNkTvWquCo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ioYF3pVtobTHmeAz/n8gdj4s99ARjOidykFtI0Ckg3R043cKy//CPCI61WU/hJNXLi0elUrZr62fSDChmHpW1x8I+BiGflvxhOoJ73G3+zI6yzl1MB2Puv/ugkkrkDA+eFSwvWX/N4p4IoiI0m1WYxTT6i/B2UygfmfEuuTgTFk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=K3Yjqy5u; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="K3Yjqy5u" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=WnA7BP+4e8CVqEwTNfcvwk1IqFPZ3MS3560LBe6L7lg=; b=K3Yjqy5uxRKSFs36qX4AknDwR7 +iMPq8WSDvuzRn22O6Efga/GWOmhRXwW9Ima21x4RxkH89CawlAzBxXc2YsIKnACYarF3JNq78Y2B +WMixFVpYP8bSH/aDBSAaXzCy2vJOv22vDTMEbxohXIk+QgWW7bXqBn+SUl33npvtasx8bwlMnte9 0b+HOgg5aX4Me5mimb4MH9iJ+APc+FzFLJy2qijWCh9SsmFscvEeKTfkABBIHsSrMpQPdYhK1uc9p 58yB5mZ8a4m5aKsstz0X1YPCGtsscTN/i7PmwvvtHu3IZB1McBw4nh8HDZ/8EqByuNzDqBdsXICfm mEBklfJQ==; Received: from 2001-1c00-8d85-4b00-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d85:4b00:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wN7rs-0000000BYT3-1IYO; Wed, 13 May 2026 11:35:12 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id EFE3B3004C9; Wed, 13 May 2026 13:35:10 +0200 (CEST) Date: Wed, 13 May 2026 13:35:10 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: mingo@kernel.org, longman@redhat.com, chenridong@huaweicloud.com, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jstultz@google.com, kprateek.nayak@amd.com, qyousef@layalina.io Subject: Re: [PATCH v2 00/10] sched: Flatten the pick Message-ID: <20260513113510.GK1889694@noisy.programming.kicks-ass.net> References: <20260511113104.563854162@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, May 12, 2026 at 10:42:33AM +0200, Vincent Guittot wrote: > I haven't reviewed the patches yet but I ran some tests with it while > testing sched latency related changes for short slice wakeup > preemption. I have some large hackbench regressions with this series > on HMP system with and without EAS. those figures are unexpected > because the benchs run on root cfs > > One example with hackbench 8 groups thread pipe > tip/sched/core tip/sched/core +this patchset +this patchset > slice 2.8ms 16ms 2.8ms 16ms > dragonboard rb5 with EAS > 0,748(+/-4,6%) 0,621(+/-3.6%) +17% 1,915(+/-7.9%) -156% > 0,689(+/- 9.1%) +8% > > radxa orion6 HMP without EAS > 0,588(+/-5.8%) 0,677(+/-5.9%) -15% 1,505(+/-10%) -156% > 1,071(+/-5.9%) -82% > > Increasing the slice partly removes regressions but tis is surprising > because the bench runs at root cfs and I thought that results will not > change in such a case D'oh :/ diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e54da4c6c945..77d0e1937f2c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9071,7 +9071,7 @@ static void wakeup_preempt_fair(struct rq *rq, struct task_struct *p, int wake_f enum preempt_wakeup_action preempt_action = PREEMPT_WAKEUP_PICK; struct task_struct *donor = rq->donor; struct sched_entity *nse, *se = &donor->se, *pse = &p->se; - struct cfs_rq *cfs_rq = task_cfs_rq(donor); + struct cfs_rq *cfs_rq = &rq->cfs; int cse_is_idle, pse_is_idle; /*