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 271B82BE03B for ; Fri, 17 Oct 2025 11:12:43 +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=1760699565; cv=none; b=qkxs/xuBUNvfKONpaffoV366iJ6U571BkAXN4udmYV9PvUvUB1ciQRi9h+yo7EgXvC7Okaf2+iyJz7+vDKHBhS1f2goyvRpzZfRDjNH6fMnV78xhW9LWkYMgm/MYfC/5JiWPTBUubaMfFx4QUA9OlXAKmC8jEtzOrc6smEMWCkc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760699565; c=relaxed/simple; bh=pIQGPKhSM5rhJpnULbKj2TOAOnhZdKVD6iAy8hQtz3o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Q0J5AmMzLl/yyBpx9bGDxTZO4tj1teLnQliLzgZrsK7VNI2dozo4uqZKjjSOBxp7jEqtfd6unTLUyP3uSymquANLKLnL6XqosfU5rgQVR3vjjju1zbNslxwsU/GFWFh2d2SV4S6Frc88MrAHA4JtQ2j7yrLdrqmg/a30yhiBBJI= 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=AUMuWmrW; arc=none smtp.client-ip=90.155.92.199 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="AUMuWmrW" 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=NbIdsWgAOxakiSHw1DpF2sYaAbTCd6lgKA726w3e14o=; b=AUMuWmrWHX/+GLnkJrFulHBxba 8HCznm0ZyLDX74mXJSB9XKamXLGe9f0+1awK1MgoqBUtWAOTJsdw2zUeYgmtHaRyON3UTqTLaH2WU xkLRWUr7gldeHarUtAqkmxgo2CBoje+yzQ3HNTDWLyI9btcTNhJI5Xe/IeyXdF5xKeydNRj7RDoAz 4upzn9axP/h9TloxlFjdD1VebJ9w4zjey/kCmATK8ze9jrvrk/ynqMPFZshU24w9LUEvBsV1PB0Yq jBTx/nztEws04MadTWUI4WyHhZMvewQB8kwcwcsDpcwA4ppOCsoZQ+MAN4Xj7FjqDLp5ZWTj+34qS Qg5uH1wA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1v9iNn-00000007W5f-1PPu; Fri, 17 Oct 2025 11:12:27 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id D81D330300D; Fri, 17 Oct 2025 13:12:23 +0200 (CEST) Date: Fri, 17 Oct 2025 13:12:23 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: LKML , Gabriele Monaco , Mathieu Desnoyers , Michael Jeanson , Jens Axboe , "Paul E. McKenney" , "Gautham R. Shenoy" , Florian Weimer , Tim Chen , TCMalloc Team Subject: Re: [patch 06/19] sched/mmcid: Prevent pointless work in mm_update_cpus_allowed() Message-ID: <20251017111223.GD4067720@noisy.programming.kicks-ass.net> References: <20251015164952.694882104@linutronix.de> <20251015172834.694547089@linutronix.de> 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: <20251015172834.694547089@linutronix.de> On Wed, Oct 15, 2025 at 07:29:34PM +0200, Thomas Gleixner wrote: > + if (!mm || READ_ONCE(mm->mm_cid.nr_cpus_allowed) == nr_cpu_ids) > return; FWIW this doesn't work on architectures that change their cpu_possible_mask around (eg. Power).