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Thu, 10 Apr 2025 07:49:11 -0700 (PDT) X-Google-Smtp-Source: AGHT+IE1Es1yXV9jGw7aSz+cHJUTqQISYOc7sxn5Z7hKD1GkHoCPRoSDNtiAfZIA4oU+uy/BcdlhWw== X-Received: by 2002:a05:600c:1e02:b0:43c:f629:66f4 with SMTP id 5b1f17b1804b1-43f2d688ca9mr39685585e9.0.1744296551259; Thu, 10 Apr 2025 07:49:11 -0700 (PDT) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([185.107.56.40]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39d89362fcbsm4928570f8f.5.2025.04.10.07.49.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Apr 2025 07:49:10 -0700 (PDT) Message-ID: <2b8a231a7eea592797bbbd853d85ef443d1e58d4.camel@redhat.com> Subject: Re: [PATCH] timers: Exclude isolated cpus from timer migation From: Gabriele Monaco To: Frederic Weisbecker , Waiman Long Cc: Thomas Gleixner , linux-kernel@vger.kernel.org Date: Thu, 10 Apr 2025 16:49:09 +0200 In-Reply-To: References: <20250410065446.57304-2-gmonaco@redhat.com> <87ecy0tob1.ffs@tglx> <2c9d71fd79d7d1cec66e48bcb87b39a874858f01.camel@redhat.com> <77988036-7550-4ee2-a738-9f9bd4417001@redhat.com> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0ByZWRoYXQuY29tPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmbiuWMCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfJzZgD/TXjnqCyqaZH/Y2w+YVbvm93WX2eqBqiVZ6VEjTuGNs8A/iPrKbzdWC7AicnK xyhmqeUWOzFx5P43S1E1dhsrLWgP Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2025-04-10 at 16:43 +0200, Frederic Weisbecker wrote: > Le Thu, Apr 10, 2025 at 10:35:55AM -0400, Waiman Long a =C3=A9crit : > > On 4/10/25 9:03 AM, Frederic Weisbecker wrote: > > > Le Thu, Apr 10, 2025 at 12:38:25PM +0200, Gabriele Monaco a =C3=A9cri= t > > > : > > > > On Thu, 2025-04-10 at 10:26 +0200, Thomas Gleixner wrote: > > > > > How can that happen? There is always at least _ONE_ > > > > > housekeeping, > > > > > non-isolated, CPU online, no? > > > > >=20 > > > > In my understanding it shouldn't, but I'm not sure there's > > > > anything > > > > preventing the user from isolating everything via cpuset. > > > > Anyway that's something no one in their mind should do, so I > > > > guess I'd > > > > just opt for the cpumask_first (or actually cpumask_any, like > > > > before > > > > the change). > > > With "nohz_full=3D..." or "isolcpus=3Dnohz,..." there is always at > > > least one > > > housekeeping CPU. But with isolcpus=3D[domain] or cpusets > > > equivalents > > > (v1 cpuset.sched_load_balance, v2 isolated partion) there is > > > nothing that > > > prevents all CPUs from being isolated. > >=20 > > Actually v2 won't allow users to isolate all the CPUs. Users can > > probably do > > that with v1's cpuset.sched_load_balance. >=20 > Perhaps, and I think isolcpus=3D can too. >=20 # vng -a isolcpus=3D0-15 cat /sys/devices/system/cpu/isolated 1-15 Seems not..