linux-kernel - Re: [PATCH v11 0/8] timers: Exclude isolated cpus from timer migration

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 for Android: free password hash cracker in your pocket

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

Message-ID: <aK9h-_1jO_pHSmLS@thinkpad2024>
Date: Wed, 27 Aug 2025 15:52:27 -0400
From: "John B. Wyatt IV" <jwyatt@...hat.com>
To: Gabriele Monaco <gmonaco@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v11 0/8] timers: Exclude isolated cpus from timer
 migration

On Fri, Aug 08, 2025 at 06:01:34PM +0200, Gabriele Monaco wrote:
> The timer migration mechanism allows active CPUs to pull timers from
> idle ones to improve the overall idle time. This is however undesired
> when CPU intensive workloads run on isolated cores, as the algorithm
> would move the timers from housekeeping to isolated cores, negatively
> affecting the isolation.
> 
> Exclude isolated cores from the timer migration algorithm, extend the
> concept of unavailable cores, currently used for offline ones, to
> isolated ones:
> * A core is unavailable if isolated or offline;
> * A core is available if non isolated and online;

Hello Gabriele,

I tested your v11 patchset against 6.17-rc1-rt1 to see if it was the same issue with rtla-onoise getting latencies in the 20,000-40000 us on RHEL 10.2. It seems to have resolved the issue. Adding my tested-by tags and test results.

rtla osnoise top -c 1 -e sched:sched_switch -s 20 -T 1 -t -d 30m -q

CPU Period       Runtime        Noise  % CPU Aval   Max Noise   Max Single          HW          NMI          IRQ      Softirq       Thread
  1 #1799     1799000003      3382675    99.81196        2840            9        1578            0      1799012            0        24369

Tested-by: John B. Wyatt IV <jwyatt@...hat.com>
Tested-by: John B. Wyatt IV <sageofredondo@...il.com>

-- 
Sincerely,
John Wyatt
Software Engineer, Core Kernel
Red Hat