From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 3609D3EDE51; Tue, 12 May 2026 18:25:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778610355; cv=none; b=IiXIQQuqX+IyN+bY2zE7uHbQTFQcSGAC56yR761vF0iOQf0MOQrFPikAmvCpbrq2dFf4dAUgS0/o6X0WEet/qoM6UyyhgsnN5GyA0LIMsYckRqpJ55ox00etdDKadmfpeninVgJsKtpGjChhH69pXHCS6KLHK2hmzQLM586qskE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778610355; c=relaxed/simple; bh=To7mJ7+Td3uQVTAjbowa0CA7iU6pgortI6FFiqIn1I8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gwLDGLZcVk62ot+B9ETWzPgcsqE9eIn6obFqMWl/LUuSvxCX9VA9EtzFq2BAAfTFOKy9XtxD8Pe3QZKUaC9NK20CMwlBdcHKX0DNZ2VTTwNxaxBnV8QaD5XDv6EEI50wWEmYs/bsQHsfmraGxe/uDUZmi89wqmxeOi5f0hzisVY= 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=p9Sm/nsk; arc=none smtp.client-ip=90.155.92.199 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="p9Sm/nsk" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=xH6WE77CT/nuZIKx6+l2ZYiqMAlpA65dKL0thlpwzHY=; b=p9Sm/nskOxQ3TunDDy7PXcG+XO RO4p9M8NgS1VmGLI+QRCQydVzg/rW6VQ66JYhwoMFNBwy3Vkhrf93jP8J2z71e1g97zG7clMmWXzy +8u6EI95XyP5IBTVLEpyUP1MQClhPyRTob7uONAwZerSfhGrQvMy6HOWnSnuMRc8eVsVb13qoynC7 4UMB1dHvB8SnTg24583+JrDKJlXz4ykQzPTwDiF7VcHPpCeOqyy3TUVosGAuXWx7/bEoBha47XBES Qka9qjZvzReTM/KTecqNrMn149qJRIEM4mFcGmIVASWNectcYfJaXawRL/V86VJ0p2ni/g8RgaN88 GZHPCb/Q==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wMrnP-0000000FcLW-2Jxn; Tue, 12 May 2026 18:25:31 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id D7069302F8E; Tue, 12 May 2026 20:25:30 +0200 (CEST) Date: Tue, 12 May 2026 20:25:30 +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: <20260512182530.GB2855641@noisy.programming.kicks-ass.net> References: <20260511113104.563854162@infradead.org> <20260512092040.GN3102624@noisy.programming.kicks-ass.net> <20260512182439.GA2855641@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: <20260512182439.GA2855641@noisy.programming.kicks-ass.net> On Tue, May 12, 2026 at 08:24:39PM +0200, Peter Zijlstra wrote: > On Tue, May 12, 2026 at 11:20:40AM +0200, 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 > > > > > > I will review the patchset and try to get what is going wrong > > > > Yeah, that is unexpected. Let me go have another look too. > > So I can reproduce even without the last patch applied. I suspect it is > in the cgroup mode patches somewhere. My first suspect is that concur > mode thing doing bad things to track the 'global' nr_running thing. Argh, n/m PEBKAC. I'll try this again in the morning :/