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 828B525B663; Wed, 31 Dec 2025 15:25:53 +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=1767194753; cv=none; b=LyKbk/rMpAYMPEaFFxgC0uuJom1D2I4BqAXaSf55F9klUgIUahAp2FHWHN0+PefkFv7eelMYZqyjaVr0gs0Xdje35QBowf9Q9WPB7oC/FDnDh8hYwv9eWa6fQK4UzwU5fzsiF9xIYcrrUA4YECCOErmHGDnr0H7vCLKWOATqKng= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767194753; c=relaxed/simple; bh=3zCSe0pygUa6B0hxj7uhQQbY3y5VvVFZcfM1W6inRQ8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qSUbMSNDHaJA/p34uAz34iuoAsQDxFYLsWElRTT3OBgpCNgIwn6JwpAJVJ/SpSBcWWlQA5KZe25PR4b53xBuWfWCeW+t268u1ecVlD25cj4XzPBqdsS3W6owFD3WUTbywVpb8zpQQznEFxjI39ud+8KgVXvdXnh4fJZxq7r4yhs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=s/MiUlto; 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="s/MiUlto" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72AAFC113D0; Wed, 31 Dec 2025 15:25:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767194753; bh=3zCSe0pygUa6B0hxj7uhQQbY3y5VvVFZcfM1W6inRQ8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s/MiUltoCktzz6D0wiCqcLuak2qC1jPP+t9uF/Wpp9NyhlhUYJRh4a7DANVK3dS3Y 5TBAIkOcZD7Uzm31uIRNg+KPXeRfrFDCHo5KImNpcVVxeo6H0CXL4UnXKcwUINX/Ll U1vQ9nn+42I+5DqP4hDp4p5tUlokQFV23MAaxYG5+JRLq2JJ2SJ1zhhHcouBH7kW4n j7tnzqkJRksmGaZ82fg+JWX+rpM1JKmvmvmVA/5WAT8i/ukuaEkGR1UaA6w9uc8YRq 7msaf9wYLApzpxDT1X8VKz50GKA//Mk01dWdH2ak+Kw+9n2yKX+4XwtHIVWi3pdEqj QbzdgFhA2MRZA== Date: Wed, 31 Dec 2025 16:25:49 +0100 From: Frederic Weisbecker To: Waiman Long Cc: LKML , Michal =?iso-8859-1?Q?Koutn=FD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Chen Ridong , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Jens Axboe , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Michal Hocko , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH 33/33] doc: Add housekeeping documentation Message-ID: References: <20251224134520.33231-1-frederic@kernel.org> <20251224134520.33231-34-frederic@kernel.org> <370149fc-1624-4a16-ac47-dd9b2dd0ed29@redhat.com> Precedence: bulk X-Mailing-List: netdev@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: <370149fc-1624-4a16-ac47-dd9b2dd0ed29@redhat.com> Le Fri, Dec 26, 2025 at 07:39:28PM -0500, Waiman Long a écrit : > On 12/24/25 8:45 AM, Frederic Weisbecker wrote: > > Signed-off-by: Frederic Weisbecker > > --- > > Documentation/core-api/housekeeping.rst | 111 ++++++++++++++++++++++++ > > Documentation/core-api/index.rst | 1 + > > 2 files changed, 112 insertions(+) > > create mode 100644 Documentation/core-api/housekeeping.rst > > > > diff --git a/Documentation/core-api/housekeeping.rst b/Documentation/core-api/housekeeping.rst > > new file mode 100644 > > index 000000000000..e5417302774c > > --- /dev/null > > +++ b/Documentation/core-api/housekeeping.rst > > @@ -0,0 +1,111 @@ > > +====================================== > > +Housekeeping > > +====================================== > > + > > + > > +CPU Isolation moves away kernel work that may otherwise run on any CPU. > > +The purpose of its related features is to reduce the OS jitter that some > > +extreme workloads can't stand, such as in some DPDK usecases. > Nit: "usecases" => "use cases" Are you sure? I'm not a native speaker but at least the kernel has established its use: $ git grep usecase | wc -l 517 > > + > > +The kernel work moved away by CPU isolation is commonly described as > > +"housekeeping" because it includes ground work that performs cleanups, > > +statistics maintainance and actions relying on them, memory release, > > +various deferrals etc... > > + > > +Sometimes housekeeping is just some unbound work (unbound workqueues, > > +unbound timers, ...) that gets easily assigned to non-isolated CPUs. > > +But sometimes housekeeping is tied to a specific CPU and requires > > +elaborated tricks to be offloaded to non-isolated CPUs (RCU_NOCB, remote > > +scheduler tick, etc...). > > + > > +Thus, a housekeeping CPU can be considered as the reverse of an isolated > > +CPU. It is simply a CPU that can execute housekeeping work. There must > > +always be at least one online housekeeping CPU at any time. The CPUs that > > +are not isolated are automatically assigned as housekeeping. > Nit: extra white spaces between "not" and "isolated". Somehow it has disappeared in my tree, some Brunaidh must have fixed that while I was sleeping. That's nice! > > diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst > > index 5eb0fbbbc323..79fe7735692e 100644 > > --- a/Documentation/core-api/index.rst > > +++ b/Documentation/core-api/index.rst > > @@ -25,6 +25,7 @@ it. > > symbol-namespaces > > asm-annotations > > real-time/index > > + housekeeping.rst > > Data structures and low-level utilities > > ======================================= > Acked-by: Waiman Long Thanks! -- Frederic Weisbecker SUSE Labs