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 829CD17A2F7 for ; Mon, 17 Mar 2025 17:44:42 +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=1742233483; cv=none; b=fE7L4xcel8upvk/BgqYt9AhQ34VBKuN23n1hFwI+F8BM1bI7L1BJPbm3yjTQGC8ygZN4C0qWeCCzVkaEzRtU/2qSHVpjikg+7JERvs3V33akV98LNYXBMyMNfxevaU8UhRpAEqzXof6zAApqf82iP+hIxRjwaRUJibrrv33BH5c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742233483; c=relaxed/simple; bh=0eV+Wt4gBgMeg5xMoR83fjBPYqPFLM8wZ5nwC5uOzQE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ECUTKpm1OQ0u6/XSsaF6lEX2peiquPwsiDIZ/p0/588/i3tEno8EGapB2KwP1qJX4ROPbLW6FcPgnYism2XmXNI1u8s3bTE4L8WQzfG8Ftzw5rmJLueQP3m2xK/aZJaA909K5Txdefdn6pwllFG+LX7Pc9kCtyBz/QsSJ/4dcTk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=jLQhNXBt; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="jLQhNXBt" 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=0eV+Wt4gBgMeg5xMoR83fjBPYqPFLM8wZ5nwC5uOzQE=; b=jLQhNXBtRpI5ZJuIvUZ758YJg3 UZBZ2ie0r7rgEzaKWV3dsaCy1/9MCBsWbXdLu9vmMdA9W00AOM1KF4PN/7aa2T2zx79JnAWILTsAs tr6IpD552Z6793zdqrXkK2WPVzmOIF7erK5S9rpdfK4vQMOipvoT/GVTRvn1gri6WXa54btuZ+xyn /lq3H3oSm1uggappEC2tgW2PJ0DnIZjea/+uPHkZFvBVEubdGqdrsvVATwQLwLZKuoy/Ojq7jkPic sOL6xqVb3atwd+YUefuA6AEnjW1OPlNY9OPLx2SoDvpUZv4XNgKWm42ZB/gkOeKwdvSYhCxWJa6Fe +4dCpzVg==; 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 (Red Hat Linux)) id 1tuEVs-00000009F0q-1WfY; Mon, 17 Mar 2025 17:44:32 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id EC2FD300783; Mon, 17 Mar 2025 18:44:31 +0100 (CET) Date: Mon, 17 Mar 2025 18:44:31 +0100 From: Peter Zijlstra To: Andrea Righi Cc: Tejun Heo , Joel Fernandes , linux-kernel@vger.kernel.org, David Vernet , Changwoo Min , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider Subject: Re: [PATCH RFC] sched_ext: Choose prev_cpu if idle and cache affine without WF_SYNC Message-ID: <20250317174431.GI6888@noisy.programming.kicks-ass.net> References: <20250317082803.3071809-1-joelagnelf@nvidia.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 Mon, Mar 17, 2025 at 06:30:57PM +0100, Andrea Righi wrote: > I guess the question is: what is more expensive in general on task wakeup? > 1) a cross-node migration or 2) running on a partially busy SMT core? That totally depends on both the workload and the actual machine :/ If you have 'fast' numa and not a very big footprint, the numa migrations aren't too bad. OTOH if you have sucky numa or your memory footprint is significant, then running on the wrong node is super painful.