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 644CA277016; Fri, 8 Aug 2025 15:50:12 +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=1754668212; cv=none; b=CHsG/ayag951KpNL96tWepuQY3/xZrH21vR4jBBzJumj1bhENTv1PaRy/lVX36FRcDeKDjad9iimAecQOfBiNvZ5lSyz/qZabAq8bSXlUj319oX72LB2we/spIg3iRLCjgq5yUrJ5/il9RYIxpVdwHbI8Y9ewPNcUxoja/x4D4I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754668212; c=relaxed/simple; bh=Fn13LnOkMLX97otRtesVk7OTraqlk5v2xVlghm+sXjQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P+mZDKYEATchViSfLZhg5hClJxv2FrOhMKVD1LUwkVR1IWtrul7SbMA5H+mOsj+8j4i+qIFuQ3sxzrBP1zmzWbmt8wZDfWStC44cvrjxeY3j4A73wCtjUW2YE8hjLSAHZogp6lnaTunjh7hC2zRTv7KeCJZJ+IOP3SUvVEHCH4k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=G3N08WGA; 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="G3N08WGA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6F73EC4CEED; Fri, 8 Aug 2025 15:50:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754668211; bh=Fn13LnOkMLX97otRtesVk7OTraqlk5v2xVlghm+sXjQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=G3N08WGAjIBlgU8eYjkiXU4FoSp9IQUU06tvK1XaWuYpVwRsqsttAs+659bFTPuXS +auLx87cNatKO5EzQ0I9q5/k1ih0wlMU3MwUYYP3uf1+SJ0XeYnfT2k8Sa/FpZhdDU z+9Yp47zXwejNZm+gIwsLY0ReTmY8eRwC3FdkHXXMvUQNg3o9cEtQqEkYwamwTwE96 GED6qrhP4zbsQeXOf/kf/CiUraKjA3WghO80D2v7GEbTa7WoPlQ1Y4jH1LUUClaNK4 Jg0Rzff93HXLu3AWlyJRY8Ph6O/RmMgpcSJbIEYZk2jNSDZ0Trq0FBGxTSqgVkjuq9 UHUWIgdWk08mA== Date: Fri, 8 Aug 2025 17:50:09 +0200 From: Frederic Weisbecker To: Waiman Long Cc: Tejun Heo , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Jonathan Corbet , "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Anna-Maria Behnsen , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Shuah Khan , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org, Phil Auld , Costa Shulyupin , Gabriele Monaco , Cestmir Kalina Subject: Re: [RFC PATCH 00/18] cgroup/cpuset: Enable runtime modification of Message-ID: References: <20250808151053.19777-1-longman@redhat.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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250808151053.19777-1-longman@redhat.com> Le Fri, Aug 08, 2025 at 11:10:44AM -0400, Waiman Long a écrit : > The "nohz_full" and "rcu_nocbs" boot command parameters can be used to > remove a lot of kernel overhead on a specific set of isolated CPUs which > can be used to run some latency/bandwidth sensitive workloads with as > little kernel disturbance/noise as possible. The problem with this mode > of operation is the fact that it is a static configuration which cannot > be changed after boot to adjust for changes in application loading. > > There is always a desire to enable runtime modification of the number > of isolated CPUs that can be dedicated to this type of demanding > workloads. This patchset is an attempt to do just that with an amount of > CPU isolation close to what can be done with the nohz_full and rcu_nocbs > boot kernel parameters. > > This patch series provides the ability to change the set of housekeeping > CPUs at run time via the cpuset isolated partition functionality. > Currently, the cpuset isolated partition is able to disable scheduler > load balancing and the CPU affinity of the unbound workqueue to avoid the > isolated CPUs. This patch series will extend that with other kernel noises > associated with the nohz_full boot command line parameter which has the > following sub-categories: > - tick > - timer > - RCU > - MISC > - WQ > - kthread Thanks for working on that, I'm about to leave for 2 weeks vacation so I won't have the time to check this until I'm back. However this series is highly conflicting with mine (cpuset/isolation: Honour kthreads preferred affinity). Your patchset even redoes things I'm doing (housekeeping cpumask update, RCU synchronization, HK_TYPE_DOMAIN to include cpusets, etc...) I have a v2 that is almost ready to post. Wouldn't it be better to wait for it and its infrastructure changes before proceeding with nohz_full? Thanks. -- Frederic Weisbecker SUSE Labs