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 A5318298CD7 for ; Fri, 23 Jan 2026 11:03:20 +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=1769166202; cv=none; b=LeeqxOoBVnVVT1SZYa0lfrD4YJ/xlh6SIEbZDtrLiHnmYIDsBIwUwDaww71sxt3yrHYwQlSH4FYmds4UZz7GucqCfqH1WeDzUZB5/BVe8s4G2OYfgxwldcq2ni0ZczZA+53xT5CmH+kG31RXyWxHkHJgiWAHPlg5zbE0E1nxAfg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769166202; c=relaxed/simple; bh=kMC82BQjP5QHcj1jDuM6gQ2sMfZROgcmIzZX5DVzEvw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Yv6q9RoZdNESKdHHNMzfsSPaX/xTUq1HXWHln8ojgRvuOZZP9zF3ArUoO8le9FB+nAPe9GHSYxzUORRgx7KLxpfpLXCHvSNELcGHI/U7ScP4fnMorEKqfanZwJ0TaAyPRnxHE7wnLwz4sbee/9ys0uJIDd/lhHsLta4pTRS0miY= 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=G6++ZnKE; 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="G6++ZnKE" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=W9ySS94wJjJQDrX3Kq9/OrD6UfxJQ/G4n9r+5XmgjuM=; b=G6++ZnKEqvHLpqCKaa1Nyrvnas BHqJsnkXClkI68iE1QASqJbqewrPvywb9tzHG3VXHLmBad/cMU7n44xZ5xMYgflrPbJFB4JAOlM/v /f3bCGhoZrtvBfD4c033W7hTGV3lpDuLT9LncBQVnvYCy1OIYyBycVEoyrAyrdhZUWu2/zgjgyhr3 BZ5cE5iYNayoediZg5I8miNQG8TknGFNFxBhPrEtC8w8YGG6jgou8/FZNWGCpwtcyTplHPZWTGZKC vaykPzsGB2lzHVYPw3MkqY3Vidv3NOH0JuOHQRgE3Q9Cf0gfKdxd+35/6b8FB6dupkkyVBDr7FkEK nm/HiPhw==; 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 #2 (Red Hat Linux)) id 1vjEwZ-00000001fZ4-3WTh; Fri, 23 Jan 2026 11:03:11 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 3ACE13007E1; Fri, 23 Jan 2026 12:03:06 +0100 (CET) Date: Fri, 23 Jan 2026 12:03:06 +0100 From: Peter Zijlstra To: Mario Roy Cc: Chris Mason , Joseph Salisbury , Adam Li , Hazem Mohamed Abuelfotoh , Josh Don , mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, kprateek.nayak@amd.com Subject: Re: [PATCH 4/4] sched/fair: Proportional newidle balance Message-ID: <20260123110306.GA217302@noisy.programming.kicks-ass.net> References: <20251107160645.929564468@infradead.org> <20251107161739.770122091@infradead.org> <8760001e-0274-454c-a4e4-1f38a9695b88@gmail.com> <20260123105046.GM171111@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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260123105046.GM171111@noisy.programming.kicks-ass.net> On Fri, Jan 23, 2026 at 11:50:46AM +0100, Peter Zijlstra wrote: > On Sun, Jan 18, 2026 at 03:46:22PM -0500, Mario Roy wrote: > > The patch "Proportional newidle balance" introduced a regression > > with Linux 6.12.65 and 6.18.5. There is noticeable regression with > > easyWave testing. [1] > > > > The CPU is AMD Threadripper 9960X CPU (24/48). I followed the source > > to install easyWave [2]. That is fetching the two tar.gz archives. > > What is the actual configuration of that chip? Is it like 3*8 or 4*6 > (CCX wise). A quick google couldn't find me the answer :/ Obviously I found it right after sending this. It's a 4x6 config. Meaning it needs newidle to balance between those 4 domains. Pratheek -- are you guys still considering that SIS_NODE thing? That worked really well for workstation chips, but there were some issues on Epyc or so. > > #!/bin/bash > > # CXXFLAGS="-O3 $CXXFLAGS" ./configure > > # make -j8 > > > > trap 'rm -f *.ssh *.idx *.log *.sshmax *.time' EXIT > > > > OMP_NUM_THREADS=48 ./src/easywave \ > >   -grid examples/e2Asean.grd -source examples/BengkuluSept2007.flt \ > >   -time 1200 > > > > > > Before results with CachyOS 6.12.63-2 and 6.18.3-2 kernels. > > So the problem is that 6.12 -> 6.18 is an enormous amount of kernel > releases :/ This patch in particular was an effort to fix a regression > caused by: > > 155213a2aed4 ("sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails") > > I'm thinking that if you revert all 4 patches of this series your > performance will be even worse? > > Anyway, my guess is that somehow this benchmark likes doing newidle even > if it is often not successful. I'll see if I can reproduce this on one > of my machine, but that might take a little while.