linux-kernel - Re: [PATCH v4 0/2] Avoid spurious freezer wakeups

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]

Date:   Tue, 26 Sep 2023 22:02:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Carlos Llamas <cmllamas@...gle.com>
Cc:     Elliot Berman <quic_eberman@...cinc.com>,
        Ingo Molnar <mingo@...hat.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Thomas Gleixner <tglx@...utronix.de>, kernel@...cinc.com,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org,
        Prakash Viswalingam <quic_prakashv@...cinc.com>
Subject: Re: [PATCH v4 0/2] Avoid spurious freezer wakeups

On Tue, Sep 26, 2023 at 04:17:33PM +0000, Carlos Llamas wrote:
> On Fri, Sep 08, 2023 at 03:49:14PM -0700, Elliot Berman wrote:
> > After commit f5d39b020809 ("freezer,sched: Rewrite core freezer logic"),
> > tasks that transition directly from TASK_FREEZABLE to TASK_FROZEN  are
> > always woken up on the thaw path. Prior to that commit, tasks could ask
> > freezer to consider them "frozen enough" via freezer_do_not_count(). The
> > commit replaced freezer_do_not_count() with a TASK_FREEZABLE state which
> > allows freezer to immediately mark the task as TASK_FROZEN without
> > waking up the task.  This is efficient for the suspend path, but on the
> > thaw path, the task is always woken up even if the task didn't need to
> > wake up and goes back to its TASK_(UN)INTERRUPTIBLE state. Although
> > these tasks are capable of handling of the wakeup, we can observe a
> > power/perf impact from the extra wakeup.
> 
> This issue is hurting the performance of our stable 6.1 releases. Does
> it make sense to backport these patches into stable branches once they
> land in mainline? I would assume we want to fix the perf regression
> there too?

Note that these patches are in tip/sched/core, slated for the next merge
window.