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 BD39C21D3CD for ; Fri, 23 Jan 2026 10:50:57 +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=1769165458; cv=none; b=bTA8CsOZCfGeblcsns01axGW/Jl1cDC8Pxk6omOGcn3ySwINGZgFpZ48LBWahXVdX6SDP4UD1WXQxTQ99DtE6lgOigKd8bur7jb2bPEZiew9jk06URil1CTMz8zr03a4HmvgqlTy2kHsRImHds+KHZ14QssvvgOzym985AAn8Wc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769165458; c=relaxed/simple; bh=FcoGmEZL2l/vU2Oe5RhKUwmrV5L8xWU98e7jIyWM1I4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VZKIZawcUNUqCsW0dcBq25VVLth2/K0KqhfGvMYLrR3CqlXz7as8NkJWEaF68Ibpy/wOLBleDx+sDFbIzUl7WZmdh6wo+8PJrsELCOgC8RwsyvKktJ4O0oM2EG9jIVq4iKsFGgZznqwVullfKOAj56hE9DmFFqI3h6w3uoMzSXw= 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=ZQ2te7sY; 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="ZQ2te7sY" 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=54xo0jtCH/X7LYbzrB4hSKDuAHhHywCYN32tnRbFqFM=; b=ZQ2te7sYLBn5GQgDhugESMAc+k Vh+zReibvwUzS7K0Hzsr6U8p/ehhUkKWYsdfQRsW61I6jBYsEAqBCrmcZYbV2K8I+FSHH/jI6NiTC 6diiIkfQj9Mc3IsDjxlnIzu0SuybOEx9nNe7RYomhITAV0AFlMacITsMEMx6+cXMebaFlKUtOi6HG YcPZjzMY4CyRfDckC+rIQEFeXdi0RdjUCW0qwQwc5MTcG764KwjukRN+/0t/MVaaxKHaSE36orbDL 7Qxot4zBZ2VkKwFy7IR7w+kHps5CEfrCcEeKngN8i5UYDNtyDTRNHgfA9/0Paz0476G/wrWoLury8 SYe2GaeA==; Received: from 2001-1c00-8d85-5700-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d85:5700:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vjEkZ-00000001etb-3Io2; Fri, 23 Jan 2026 10:50:47 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C80013007E1; Fri, 23 Jan 2026 11:50:46 +0100 (CET) Date: Fri, 23 Jan 2026 11:50:46 +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: <20260123105046.GM171111@noisy.programming.kicks-ass.net> References: <20251107160645.929564468@infradead.org> <20251107161739.770122091@infradead.org> <8760001e-0274-454c-a4e4-1f38a9695b88@gmail.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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8760001e-0274-454c-a4e4-1f38a9695b88@gmail.com> 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 :/ > #!/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.