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 DF4BE2773FF for ; Thu, 29 Jan 2026 09:24:20 +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=1769678663; cv=none; b=f3s779o8XXTtKBIrIWIbnX/CXCpagWw7AKNAJKvTBZB+W2YstBXz4PifFsiBEwWaWAJGK5d/P5Bvh3musHxCOCtvU7sqgz3Ja8QfdrlAIYqzZt7MrcJhdaVoCEzcsNnO5p2e1JR6X6IP9NkBTjdHxyI1THH2RDyynSyQwBChOpU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769678663; c=relaxed/simple; bh=z9xSkAcdICcORVbp8fzQV8pcyqDydpwSPkqj+8RD+88=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ft++m7FXbUboO+eK291gysdKuXRgN1v146SAePIfRNZZGP4syQztdKGTdGApExkkyQDMTcVFQJJOZdSHQ2pdSLZDJt1WWJxVSPQN8aMjUXbuK7VqvueIoksHRylVW5zUt0Qh9gIasjDubVBynlAd0rU3g1cbr3/K/IGqYLHF05o= 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=FrEkbp8j; arc=none smtp.client-ip=90.155.92.199 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="FrEkbp8j" 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=3qAOBNRnYzDWKIh+AXLg8ekwWOpIwI5gNdxPriBb2R4=; b=FrEkbp8jIR3JEMjqlWKK2pq4x6 RbOB1oUrvgsjBS55QFNt6Un/EYHmFHttIf7Dj09Nj3lMBQkfeTeUFHVP70sng0Vr4Y6zVIBJIm0q0 qixTs4/LuqofrpHaHbJ7szT2rgwracHPQNTD07HFWia/0EQRYAaJxCY+/f9TtCPAw9vAiliuPCZmO XqV+OT5MfnRpxncBW6xanNI10HgDjY+1bSXC8ePJz0Lz3DR1/SZZRnZyxq80P3TJPp1gL5gVIhLT/ 1CWRyycEtRf961qhontIXf02DX/3ovd7d+z5OYH7RFIpZi3HZ07Mf8s91kmqreMLPmE+2TMPjsZVN xBx5r0Kw==; 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 desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vlOG1-0000000A7c1-3eKd; Thu, 29 Jan 2026 09:24:10 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 2549F300754; Thu, 29 Jan 2026 10:24:08 +0100 (CET) Date: Thu, 29 Jan 2026 10:24:08 +0100 From: Peter Zijlstra To: "Mohamed Abuelfotoh, Hazem" Cc: Mario Roy , Chris Mason , Joseph Salisbury , Adam Li , 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 Subject: Re: [PATCH 4/4] sched/fair: Proportional newidle balance Message-ID: <20260129092408.GE217302@noisy.programming.kicks-ass.net> References: <20251107160645.929564468@infradead.org> <20251107161739.770122091@infradead.org> <8760001e-0274-454c-a4e4-1f38a9695b88@gmail.com> <3ef2a178-db96-4a2c-9e74-44ba81bef030@amazon.com> <20260127084412.GV171111@noisy.programming.kicks-ass.net> <20260129091937.GY166857@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: <20260129091937.GY166857@noisy.programming.kicks-ass.net> On Thu, Jan 29, 2026 at 10:19:37AM +0100, Peter Zijlstra wrote: > On Wed, Jan 28, 2026 at 03:48:13PM +0000, Mohamed Abuelfotoh, Hazem wrote: > > > Below are the hardware specs for both c7i.4xlarge & c7a.4xlarge. > > > > c7i.4xlarge > > > > CPU Model: Intel(R) Xeon(R) Platinum 8488C > > Number of CPUs: 16 > > Memory: 32 GB > > Number of sockets: 1 > > But the 8488C is a 56 core part, with 112 threads. So you're handing out > 8 core partitions of that thing, for 7 such instances on one machine? > > (Also, calling anything 16 core with 32GB 'large' is laughable, that's > laptop territory.) Also, are you employing Intel-CAT on these partitions to separate the L3s? (Not immediately relevant I suppose, but I was curious) > > ------------------------------------------------------------------------- > > > > c7a.4xlarge > > > > CPU Model: AMD EPYC 9R14 > > Number of CPUs: 16 > > Memory: 32 GB > > Number of sockets: 1 > > And that 9r14 is a 96 core part, 12 CCDs, 8 cores each. So you're again > handing out partitions of that. > > > > For both cases, are these partitions fixed? Specifically in the AMD case, > are you handing out exactly 1 CCDs per partition? > > Because if so, I'm mighty confused by the results. 8 cores, 16 threads > is exactly one CCD worth of Zen4 and should therefore be a single L3 and > behave exactly like the Intel thing. > > Something is missing here.