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 AA47F396D13; Mon, 18 May 2026 21:13:28 +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=1779138811; cv=none; b=V8PfUsWdBTbe9kcoSFX2TbHHhXcP2uoVA4omVNsUXFeZE8N3kw76NGqbdcptAjGAD0GXvWiE5CypAue0AlO/fycbns4SCrSzD2b07P5sI4Djk+TVhgMQi7+dafERkVuNdpUR+OZRZpyJIH/oOrLBPMldNoEK3ickpqOteL00DX0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779138811; c=relaxed/simple; bh=glRPy+T3VEld++JNwI+fJqBcRVqxWeoNhk7d0ihJb8c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lXwikN8vzy/Qj0IAR8IMADduDNv+8WQW2aWer0OIOLTkmzCISK1e49cZ5t4lGWH0NqqEMD27MsB6VQm+CTHMRk7dzxf0Ae3TBaKELLdVTcLKlzuDQBdNr8U83EjsMq1bgKYNXl4vTDDyqRT+FMbmf1Zkjb+yYrmzUm9QUzlezqE= 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=SH1WblC4; 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="SH1WblC4" 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=sOXgvOxiplvVHt7xJfFoPCb1TYYOJKSYO19fq+Z0iVc=; b=SH1WblC4BadfsMpE43wE/rmNzU FrpgNk4m+Do+178jV55ySubE2cc+rZzt84oLy7AQR7Fa25Awv9K8UXynTcXpluAJxLg4nYqpgpdYB vA4FTMN6VygqAgzQ7CjkvJ/ZkCL5lMA28HFA10y/KB+N2rBXYugF4CKl/SzkQf7uVbUsQJjkM8ivQ BwSkWFabJq3WN4tm4EBmZ9bDO+c84unDpJf+mE4+gmZzzcSxEORCYL8UfnEcX4mVd8W5JiZydVjlF emJWO9m7pmiIA3/HIdK+qGzbgpX46ax6LuGqt0FW05HT2guB+HKnhHX2PeLAEnx/8SGW+Uu4C+Qv2 bHWjPtBQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wP5GT-000000059IJ-1mMP; Mon, 18 May 2026 21:12:41 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id E6F9D3007A4; Mon, 18 May 2026 23:12:39 +0200 (CEST) Date: Mon, 18 May 2026 23:12:39 +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: <20260518211239.GY3102624@noisy.programming.kicks-ass.net> References: <20260511113104.563854162@infradead.org> <20260513113510.GK1889694@noisy.programming.kicks-ass.net> 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 Mon, May 18, 2026 at 03:34:51PM +0200, Vincent Guittot wrote: > On Wed, 13 May 2026 at 13:35, Peter Zijlstra wrote: > > > > 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; > > I tested this patch on top of the series but it doesn't fix the perf > regression on rb5 > > hackbench 8 groups thread pipe is still at 1.907(+/-7.6%) with default > slice duration Weird, I can't reproduce anymore with this fixed :/ I'll try more hackbench variants tomorrow I suppose.