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 F34E417A2EC for ; Mon, 17 Mar 2025 17:25:46 +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=1742232349; cv=none; b=RVdcSzbY0H/szf5IE3wzWbgovCXUyFTCwbqQS2MuaRghfUxuh9zOmDmI2li9rBvyJIaDDrg92oJhz43G37HnaTcp+r4uKrlKfpG0IsAHqf6D2iDAKlo6yuVZLh123CvYeMu/iPzl1yQ2LkRLkfcCVaPRjHVw//hJtBpoP4B1Qm0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742232349; c=relaxed/simple; bh=+m2o+1RkSSOS1CRqKraRDIxQJJtaGzOP34fmPu6Y5vQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=W3rm1iU9K7Uurbb68c+paz69quvmd5jMKh/tP3nOlW76SdFcW1lILxAvF58EwClcpVzMY2yXeaurqoBs2t09KcHhC1fxn4ShjYBfYnKuIWw9hHu3fxroUyEfd749x2D4f9nFw0LWxLYiU+NCH6++wLhizfYo8kf3BlXUcVphWAA= 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=ZIPI0mIx; arc=none smtp.client-ip=90.155.50.34 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="ZIPI0mIx" 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=3T7MbICDWLqXG/IN46NNRXZBn6qTa6XHFg3bjRm1Tq0=; b=ZIPI0mIxMkmottMyMF+LBoVDxe gx/1COr+rWQvcA708SpcFZeyqRE9Ak1Klk1q+Ji65JX+nG9KDCh3cGPGYfmKOH0YpzLcTG2X9Uoid NYI6lfLPTW5COm7cmtLgqjjJNGm1LHpasDm+bWVYC/2niEizCMwB4CF6fhOpSyFURf/r3rN0U5k3E KzTnN+xTtUawXnRJTbwMzrPsWjKdhqrPMjlh4AJ9guKcesqEn8i2IWX5HMBPkGsxqsY1FZxV8RJ5H TjrfQhDiVaCIkaTsV3tMwzQ0dKhWrTkUvYjP9PXbvJTgHsMTYUvaiJgbXABoWkcMtvCMNrlRGgbPB 3Q/Bf9MQ==; 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 4.98 #2 (Red Hat Linux)) id 1tuEDZ-00000009CqT-2Y8f; Mon, 17 Mar 2025 17:25:37 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id CBC3E3004AF; Mon, 17 Mar 2025 18:25:36 +0100 (CET) Date: Mon, 17 Mar 2025 18:25:36 +0100 From: Peter Zijlstra To: K Prateek Nayak Cc: Ingo Molnar , Juri Lelli , Vincent Guittot , Chen Yu , linux-kernel@vger.kernel.org, Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , David Vernet , "Gautham R. Shenoy" , Swapnil Sapkal , Shrikanth Hegde Subject: Re: [RFC PATCH 0/8] sched/fair: Propagate load balancing stats up the sched domain hierarchy Message-ID: <20250317172536.GF6888@noisy.programming.kicks-ass.net> References: <20250313093746.6760-1-kprateek.nayak@amd.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: <20250313093746.6760-1-kprateek.nayak@amd.com> On Thu, Mar 13, 2025 at 09:37:38AM +0000, K Prateek Nayak wrote: > tl;dr > > This prototype is currently limited in the sense that it can only reuse > statistics for busy load balancing. Reusing stats for newidle load > balancing specifically ran into issues elaborated below. Right, it makes sense for busy load balance, newidle I think: > David had proposed SHARED_RUNQ [4] to improve on the shortcomings of > newidle balance for Meta's production workloads. we need to look at this again. Something around the EEVDF merge made the thing unhappy -- if we figure out what and fix it, I think this makes more sense than trying to optimize the current scheme for newidle. newidle really is about getting *any* work fast, which is a totally different game than the regular busy balancing. Anyway, I'll try and have a look through the patches.