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 ED99237F8CF for ; Thu, 29 Jan 2026 09:19:55 +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=1769678400; cv=none; b=siqMmcQKk8CXccm/6m+BkTvyr8xZR+4S6m+ZJHPLvLB7XSK6jecz7xKEi94SA/54A1Kf+29riwWJxdrpLEtGg9dtIHrj+6Jc17joS0DTLzA+CYodQSp3syqkos5pTLtxERgFFH2H1Jj6fpl1M33eSC8K1gj4Q1K6EvSffHb/BHA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769678400; c=relaxed/simple; bh=5f94LI02y+N/zRuKlMeP+QQ7t3nupM19v4BKqxkrCFI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=e+Uyd23rAff2ja44/aGxtMiKGqkE+PolH81tV/07wWIu9zj9VcEpan108A7iMI8hAfFZIBwkDTth8hFmGdCrVDvkzf+Ww7X4Ci73+80VZ+WlyHj3YWlLGuMW11cINGVX+sOQeluWzl3G4kyBtVFmsBWDhZybkzmg2/li5i1Vjfs= 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=f4JcyTkP; 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="f4JcyTkP" 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=PBO65MugJlBIa9Dx65Dk5FlrQ4KKU18j+CqxjOg+2wY=; b=f4JcyTkPVgrpJKC0Ax52Jst87z iZ8dIgxsHfU6R4Nt6rBeI9BFBRWwNEnaZIFfmUS95BB64s6mQbsFQtwmgMboauJ6Oa0EPXKo7Pd2Y TVy87/PCl7AUK3Ti3NycVG8ufN0Ohe7J216HOplRpUbIxL7h/r3VgMMXszslmqn4PFCT9lLqCkJ+W HmbD1RH0fwR55wT3iqN20pzMcJ0zYJLWDcSkDuqiMCeJAXn2M6yVSJ4p7E0aPrx5LpHXFVzknbwBP N4hjsSd1ntOI7Fevw4eCPasx8QqrH4TMWEweGwF/PMtKUbny/m6u2QkZMnjZYS8ZPnJBZkYE0mhHp c0iEPQsQ==; 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 1vlOBk-0000000AS0r-1YXp; Thu, 29 Jan 2026 09:19:44 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C5D45300E8B; Thu, 29 Jan 2026 10:19:37 +0100 (CET) Date: Thu, 29 Jan 2026 10:19:37 +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: <20260129091937.GY166857@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> 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: 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.) > ------------------------------------------------------------------------- > > 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.