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 D533936C9D0; Tue, 12 May 2026 18:25:06 +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=1778610310; cv=none; b=OPHUP/0rJ4mU8hZ7b9hBMkZuakkAV/Zc/0UlGYqUwBd029lz9ahnDoQuhWJ7Djmpvu9fdqlMqDT3VI29UrqMtd9ziJgTza0Lk2mYg5dtEzhEg8A/QSUKmCKUizSISewn6w24MS1u1TCaq4E4GpVnbi9zF0mlAaPoM7TflmAv9Ic= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778610310; c=relaxed/simple; bh=wWFplwI8P2hR6V1buCzgG+m8ARlADkfCV0zPnRB0cqc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GuapYwg3e8AvTS65jfz+iCIKDJAiARGoSUgPcD1b6Dl7p/3KoKKJwM6eLjJid9kdbINiOmd2OYO8328xkkaqPwqUU6Fszadtcfqx7+tiKHBJRwFfP5SY+J5cYR5nuzVznIHnA6Fo5D2zWYjTxSi3yYQagtwd9Icixk8VNjUkGY0= 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=Rg2TBN2T; 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="Rg2TBN2T" 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=iTtNV5Ij0ZGs+MxSCL8DE835b24AdzqfLKn3z0XFiqM=; b=Rg2TBN2Tgmw6UhYaGPLNSJ9A5/ ofkZ4FwFUUF5YBoiDSUZCvSkqTVG8QPodYvuWvGt3jZhyqc8BBRP8nUcmPt6zAUlMwa6U/UDYARoJ cNZKURIedo2UVXFIY/iZcT/coBTtml1Gd+ApxvcxBojnKQ2/yPMjEqD9ycSEoaYpoiDMu/81G5V0T YD15I59HOTzAbM+YdbPLAQ+3QXYz0kSfO8auU6c/Zw71xngYui4BKitt1wCrBoDS2W4czuPrg/THp 007QD+YRFfBMLkVjb5hEmVpbTlG0STIkXNI246B1A76MNsdxD72huF9X2cZI6xUdwcQp9mba6GZEr 7TirtqZA==; 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 1wMrmb-0000000AAb0-0NoG; Tue, 12 May 2026 18:24:41 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id BD04F3013A0; Tue, 12 May 2026 20:24:39 +0200 (CEST) Date: Tue, 12 May 2026 20:24:39 +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: <20260512182439.GA2855641@noisy.programming.kicks-ass.net> References: <20260511113104.563854162@infradead.org> <20260512092040.GN3102624@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: <20260512092040.GN3102624@noisy.programming.kicks-ass.net> 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.