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 F01C52EBB98 for ; Fri, 20 Jun 2025 16:08:48 +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=1750435729; cv=none; b=hKUGQzH5Zeky9rkFOMR8PBZzhDd1pdsvTtexwHBbqO7xbw5vvOEwjpt5oGaAMbXekzAk5zRDYYlkP/VbAcdjJU/GMi5VBQ1rs2LnOOvmjcMOAqXrAQ6Abb9IYPIZ9Hg2t9+tHzOEuptNwhNv9avjFOKVjPkfX/eXYUPIawUpKxk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750435729; c=relaxed/simple; bh=w3Tx/FY33b4U6ZvjGO5LWtC9nOYxPo8arMmytfpBgHw=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=seIFE7+w4i2xno9UOtrnh90wkWrma62jM2BIlA//sN409klC3TFEoLWnnFzFs8PktffcNMtakb8NtOLmI0zbgEE+waov8uL42RIJMOnVa4AIWAITzQXAs/vSOlceGJOeI7HXcH/X1xQQpEP8+Jo9U3K4grv7viZdGOUSSRikMpA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lrKUQYcG; 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="lrKUQYcG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C852C4CEE3; Fri, 20 Jun 2025 16:08:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750435728; bh=w3Tx/FY33b4U6ZvjGO5LWtC9nOYxPo8arMmytfpBgHw=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=lrKUQYcGXy6XrXCt1Vw/I2l2VEnU4Z37QD6gPUSu0xWrB/G3LMi5Tfv3j9Z2LJd3z HCjWyjLeB2LriOmjlbxyO90H9U9kc/ebySxF4nrHtVg0oodO3F2OBA6qGSNwqjHRmA L0tCwpMP++5VtrjDO9tLSbTpZMZ1FoEF4xXCt2WW2AWrsalnQcZtsEi0ZxTqfNYf3n GDhCEhITW2sX1igYUguSosS1WzVlQhRXEDQFFXAlb7MjTy4mXfhDmAFyP971kNVXum cx+k6U32pO8NIToiI2M1vl+iDOtIR2SpzyeQ6XPbqX7yABEi4/a3Xlq379QF3YPYiP 3lqHb8+kfuf0g== Date: Fri, 20 Jun 2025 11:08:47 -0500 From: Bjorn Helgaas To: Frederic Weisbecker 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: <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=us-ascii Content-Disposition: inline In-Reply-To: <20250620152308.27492-1-frederic@kernel.org> 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. Bjorn