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 CFED122D7B9 for ; Fri, 3 Jul 2026 16:54:29 +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=1783097672; cv=none; b=GLKXC8TRNhBzzs0JD/BNWxFKz7TxU2paPXkMfDcevebU9WaoUjqXn5E2SrMMjuNq9PU1F15tkkxApEjxJq2x9P9YCXl2U3rDx5GsvP8WKAEr8dk7ZLMVWiM/Onl2aPJKjPHlcJiDzdPwupLm0rAb5/YBz/jJHTLyKT5J1spJAK0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783097672; c=relaxed/simple; bh=jL+7J5R+L2cwZGA8k5SwIOLhxEhp4xkwjPkQH/FhvCo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dE56nOz7NiqwOhjA4zaalRe/pKI+aQJbjl4DUmyXtHi/BhUwBZTw69K3bYJoODP5eCJsfDVpOcOEB62AczuBnnPbcrN2cL3/AOjtG/31Yo3lpMFOzjMLAzoan8yQMqvfWmwpIhI34FnCXyuApN2LoCFBJnWQIb+PdbtlTqslbx0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Xsj8nqdb; 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=pass 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="Xsj8nqdb" 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=jL+7J5R+L2cwZGA8k5SwIOLhxEhp4xkwjPkQH/FhvCo=; b=Xsj8nqdb4sAdmI2NZdd7XYFN2N /mZ3eIdrFzN6Sx0DwoXk4lCsRs3gTGjyGw5Xi2K+1VeLYdbhTBxz6qlaYTnIkZFT+QCzGq8aRLKW1 twg449yy0LmNPuoIzm3LQma+qfIvLOQ2RTaSgsbkJGQFHVMJ6abfpQ5MigFeV9mcWeldChh9TkMFA tS4fW+uLW/A9TVd04UmlPI+NYMgGVjZmgUMrg8HF7pJdeNf2Wzm4xzsiiArYh69pESg9N1H2eU5NI 37yCPnx6VR2RcgnvIRIGGGEA/273omFtAQTIq3e1/ClYuzv/DSOcQ2fNUVZ68IPKUmVAwrWDhPsYV VeUCQBkA==; 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 4.99.1 #2 (Red Hat Linux)) id 1wfh9b-0000000AbPQ-16wp; Fri, 03 Jul 2026 16:54:15 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 4E8B330035C; Fri, 03 Jul 2026 18:54:14 +0200 (CEST) Date: Fri, 3 Jul 2026 18:54:14 +0200 From: Peter Zijlstra To: Andrea Righi Cc: Christian Loehle , K Prateek Nayak , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Ricardo Neri , Shrikanth Hegde , Felix Abecassis , Joel Fernandes , Phil Auld , linux-kernel@vger.kernel.org, Julia Lawall Subject: Re: [PATCH] sched/fair: Stabilize idle SMT core selection with asym-capacity Message-ID: <20260703165414.GR751831@noisy.programming.kicks-ass.net> References: <20260630152747.128746-1-arighi@nvidia.com> <2ed258a2-ac9f-413b-aa39-59a59cdee1fe@arm.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: On Fri, Jul 03, 2026 at 04:52:17PM +0200, Andrea Righi wrote: > As mentioned in my other email, I found a surprising asymmetry on this machine: > pinning one worker per core to the first SMT siblings gives substantially better > performance than pinning them to the second siblings, despite firmware > advertising identical capacity and frequency for both. Cute, that's something that Power7 also had. That's where SD_ASYM_PACKING originated from.