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Wyatt IV" Cc: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Thomas Gleixner , Waiman Long , Tejun Heo , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= , cgroups@vger.kernel.org, "John B. Wyatt IV" Message-ID: <59a5840f-2754-4478-8c4d-ffca02b1ecf1@redhat.com> In-Reply-To: References: <20250915145920.140180-11-gmonaco@redhat.com> <20250915145920.140180-20-gmonaco@redhat.com> Subject: Re: [PATCH v12 9/9] timers: Exclude isolated cpus from timer migration 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=UTF-8 Content-Transfer-Encoding: quoted-printable X-Correlation-ID: <59a5840f-2754-4478-8c4d-ffca02b1ecf1@redhat.com> 2025-09-15T20:51:21Z John B. Wyatt IV : > On Mon, Sep 15, 2025 at 04:59:30PM +0200, Gabriele Monaco wrote: > > Your patchset continues to pass when applied against v6.17-rc4-rt3 on a > preview of RHEL 10.2. > > rtla osnoise top -c 1 -e sched:sched_switch -s 20 -T 1 -t -d 30m -q > > duration:=C2=A0=C2=A0 0 00:30:00 | time is in us > CPU Period=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Runtime=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 Noise=C2=A0 % CPU Aval=C2=A0=C2=A0 Max Noise=C2=A0= =C2=A0 Max Single=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 HW= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 NMI=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 IRQ=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 S= oftirq=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Thread > =C2=A0 1 #1799=C2=A0=C2=A0=C2=A0=C2=A0 1799000001=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 3351316=C2=A0=C2=A0=C2=A0 99.81371=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 2336=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 9=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 400=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 1799011=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 23795 > >> This effect was noticed on a 128 cores machine running oslat on the >> isolated cores (1-31,33-63,65-95,97-127). The tool monopolises CPUs, >> and the CPU with lowest count in a timer migration hierarchy (here 1 >> and 65) appears as always active and continuously pulls global timers, >> from the housekeeping CPUs. This ends up moving driver work (e.g. >> delayed work) to isolated CPUs and causes latency spikes: >> > > If you do another version; you may want to amend the cover letter to incl= ude > this affect can be noticed with a machine with as few as 20cores/40thread= s > with isocpus set to: 1-9,11-39 with rtla-osnoise-top > > Tested-by: John B. Wyatt IV > Tested-by: John B. Wyatt IV > Thanks John for testing again, I'll mention your results with the next vers= ion. Cheers, Gabriele