linux-kernel - Re: [PATCH 00/27] cpuset/isolation: Honour kthreads preferred affinity

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aF1f7aBSzyk7vJty@localhost.localdomain>
Date: Thu, 26 Jun 2025 16:57:49 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>,
	Peter Zijlstra <peterz@...radead.org>, Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>, Waiman Long <longman@...hat.com>
Subject: Re: [PATCH 00/27] cpuset/isolation: Honour kthreads preferred
 affinity

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