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 1A2B227453; Wed, 30 Apr 2025 10:03:09 +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=1746007391; cv=none; b=MMrfyhhpdKetNJ+K3lHvlb8m9YSIQmRpYhxiMfxVNIxq5GiolfcyDPw/Nt64fWVvMOD+xF2K5kOBz0plOABnOvhvlE955tDjDit4rJmVEYHZmffgIIguezVRgTpXBpRIvqeXJ3wgGY5ami3RXlUb2rgaoWiJiNcvRlDXV6hvO9Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746007391; c=relaxed/simple; bh=KGrywym0ZOPJ7Xz6jT1rH9HD67hby50/YM/sqq5W7Ew=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=B5J07/oTVnO5SVSpmXtCOkMu5XcI5X+Zi4VyX+nm2/WvUVQnw4GPlztzIYhCCOKjPr5DKOdXwqcES9I1Ld5dkv+X4kYhBIh0BMoh6LIE1YyGQqncPkWIKUJ/FD2KMoG+r//YatckdRVF8bp0ii1Xgg0eABQErEI3G0+nQF5nWpY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=iPP1cP0b; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="iPP1cP0b" 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=wnpd3q5WOijzfJQLTLp3KY3bMqG+b+asGNrhRbSKFUs=; b=iPP1cP0bFtD3Rv3xLAGyffUDiZ KKZU3/5OI9Imh0rKeKe7yM+m7wFhp2kvOPllhKaxzyJTuWhpIdA6tb1oowm84bawgx8wd02qNu6cR 4EVMvZn1Fl9QCCzoXuYLo5HmbJXplPthuBzppxOog5bkXxNqG2qm5JL0IR+YGf/ReBl+vKg4vFE8z txEh+QdtASPET3fCX8boA2V+WUmWH98O1aUY9MjhQiznUoXd7uN0/1jMZwL5U77RpDfQUlDvMCxPS aSXYdFnpcc9NRg4FrtWUS3zd7PmwgClqpdOZBHmZd8MbUJoWrv1ezKD8UMB+DLyw7Up7nvGUb/0Tw y0KgRDMw==; 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 4.98.1 #2 (Red Hat Linux)) id 1uA4HL-0000000DlSm-2vRX; Wed, 30 Apr 2025 10:03:00 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 3A8AB300642; Wed, 30 Apr 2025 12:02:59 +0200 (CEST) Date: Wed, 30 Apr 2025 12:02:59 +0200 From: Peter Zijlstra To: Cristian Prundeanu Cc: K Prateek Nayak , Hazem Mohamed Abuelfotoh , Ali Saidi , Benjamin Herrenschmidt , Geoff Blake , Csaba Csoma , Bjoern Doebel , Gautham Shenoy , Swapnil Sapkal , Joseph Salisbury , Dietmar Eggemann , Ingo Molnar , Linus Torvalds , Borislav Petkov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, x86@kernel.org Subject: Re: EEVDF regression still exists Message-ID: <20250430100259.GK4439@noisy.programming.kicks-ass.net> References: <20250429213817.65651-1-cpru@amazon.com> 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: <20250429213817.65651-1-cpru@amazon.com> On Tue, Apr 29, 2025 at 04:38:17PM -0500, Cristian Prundeanu wrote: > [1] https://github.com/aws/repro-collection/blob/main/repros/repro-mysql-EEVDF-regression/results/20250428/README.md That 'perf sched stats diff' output is completely broken -- probably trying to diff two different schedstat versions isn't working. Anyway, looking at the two individual reports side by side: - schedule() left the processor idle -- is up vs. - pull_task() count on cpu newly idle -- is down - load_balance() success count on cpu newly idle -- is down Which seem related and would suggest we look at newidle balance. One of the things we've seen before is that newidle was affected by the shorter slice of EEVDF. But it is also quite possible something changed in the load-balancer here. Also of note is that .15 seems to have a lower number of 'ttwu() was called to wake up on the local cpu' -- which I'm not quite sure how to rhyme with the previous observation. The newidle thing seems to suggest not enough migrations, while this would suggest too many migrations.