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Wyatt IV" To: Gabriele Monaco Cc: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Subject: Re: [PATCH v11 0/8] timers: Exclude isolated cpus from timer migration Message-ID: References: <20250808160142.103852-1-gmonaco@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=us-ascii Content-Disposition: inline In-Reply-To: <20250808160142.103852-1-gmonaco@redhat.com> 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 Tested-by: John B. Wyatt IV -- Sincerely, John Wyatt Software Engineer, Core Kernel Red Hat