From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3D3352ECD22 for ; Thu, 26 Jun 2025 14:57:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750949872; cv=none; b=dwLJMRcdPYOIWUn/bW/Oy8ToBr+4OvdH5rtTuTzhQqseT0P80DXGBQ+r3TQp5+esTOEf7LMx5uyt/DHnYxUMnl9hqP4F3aaLAtwKH1HWs6YMBv9RdYEh1yk0KsRW2OywRdCZiR335iJ4SmRTAe5am/e1veQcwEofPQUqMh56vNY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750949872; c=relaxed/simple; bh=waAzfhSPPgiKKjNY60AGgeGRs4IxNy8v7C7OpSqOHIg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GWV8unA/bCZZ/bS6yN4xJHGwiwL6Rhu1/O4axXaeWAlikb9kb0Y1e3jpYR4J5Y7TVoA9PrJYp+CAusGfb3Je7NqJcWR4HN/xTCZrjJSzmbknEL5F9dtFi0/zVBvILkWLrVZmIjf5Ol5bOQB6ZEEuH0Ea5gdyAU99OqWsPxWHVqs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NO9uKOtt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NO9uKOtt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71A94C4CEED; Thu, 26 Jun 2025 14:57:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750949871; bh=waAzfhSPPgiKKjNY60AGgeGRs4IxNy8v7C7OpSqOHIg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NO9uKOtt6sMCYoYTXoGQpqBh/nAlDOrbMErluIN9jtHeN5hmOCdtI7Gk1kc0/Qp5K QXrC2Hfn4eC16tnB5nD0z0zr68jgwlcd0Ev/kkWZ9vDzIdj0hUqm2k05UxGygugPzP 6nmZu3MNvUS2BX1oxbQKz3Ake1wa6wjMOkIKLphHOGtMmM6buKojNKA3fTkmY3I0FK Pj/QZRu2DLHtBdgmVjlG+Wdk7SLF9nacf3T5dAUinj1qdK5mb+pwQVxNRvFh10kOJf skmhl25nOpnOO6KIfMDymA2R8feriSFj9ejZ0pTw4Vf1FGuvTD07eLuMwixaCYpa94 EwZYvBUGH35+Q== Date: Thu, 26 Jun 2025 16:57:49 +0200 From: Frederic Weisbecker To: Bjorn Helgaas Cc: LKML , Marco Crivellari , Michal Hocko , Peter Zijlstra , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Waiman Long Subject: Re: [PATCH 00/27] cpuset/isolation: Honour kthreads preferred affinity Message-ID: References: <20250620152308.27492-1-frederic@kernel.org> <20250620160847.GA1295810@bhelgaas> 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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250620160847.GA1295810@bhelgaas> Le Fri, Jun 20, 2025 at 11:08:47AM -0500, Bjorn Helgaas a écrit : > On Fri, Jun 20, 2025 at 05:22:41PM +0200, Frederic Weisbecker wrote: > > The kthread code was enhanced lately to provide an infrastructure which > > manages the preferred affinity of unbound kthreads (node or custom > > cpumask) against housekeeping constraints and CPU hotplug events. > > > > One crucial missing piece is cpuset: when an isolated partition is > > created, deleted, or its CPUs updated, all the unbound kthreads in the > > top cpuset are affine to _all_ the non-isolated CPUs, possibly breaking > > their preferred affinity along the way > > > > Solve this with performing the kthreads affinity update from cpuset to > > the kthreads consolidated relevant code instead so that preferred > > affinities are honoured. > > > > The dispatch of the new cpumasks to workqueues and kthreads is performed > > by housekeeping, as per the nice Tejun's suggestion. > > > > As a welcome side effect, HK_TYPE_DOMAIN then integrates both the set > > from isolcpus= and cpuset isolated partitions. Housekeeping cpumasks are > > now modifyable with specific synchronization. A big step toward making > > nohz_full= also mutable through cpuset in the future. > > Is there anything in Documentation/ that covers the "housekeeping" > feature (and isolation in general) and how to use it? I see a few > mentions in kernel-parameters.txt and kernel-per-CPU-kthreads.rst, but > they are only incidental. Not yet, I'll try that for the next take. Thanks. -- Frederic Weisbecker SUSE Labs