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Mon, 09 Nov 2026 19:15:56 -0800 (PST) Received: from smtpclient.apple ([103.243.98.37]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b16797069bsm1826210a91.14.2026.11.09.19.15.44 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 09 Nov 2026 19:15:56 -0800 (PST) Content-Type: text/plain; charset=us-ascii X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.700.51.1.3\)) Subject: Re: [PATCH 0/6] sched: Expose writable interface for preferred CPUs mask From: Maxim Kuvyrkov In-Reply-To: <20261101192203.6979-1-ynorov@nvidia.com> Date: Tue, 10 Nov 2026 16:15:31 +1300 Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Juri Lelli , Vincent Guittot , Shrikanth Hegde , Yury Norov , "Rafael J. Wysocki" , Alexander Gordeev , Andrea Righi , Ben Segall , Christian Borntraeger , Danilo Krummrich , Dietmar Eggemann , Greg Kroah-Hartman , Heiko Carstens , Johan Hovold , Jonathan Corbet , K Prateek Nayak , Mel Gorman , Mete Durlu , Randy Dunlap , Rasmus Villemoes , Shuah Khan , Steven Rostedt , Sven Schnelle , Valentin Schneider , Vasily Gorbik , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, driver-core@lists.linux.dev, linux-s390@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20261101192203.6979-1-ynorov@nvidia.com> To: Yury Norov X-Mailer: Apple Mail (2.3864.700.51.1.3) > On Nov 2, 2026, at 08:21, Yury Norov wrote: >=20 > The preferred CPU mask currently lets the steal governor reduce vCPU > demand when physical CPUs are contended. This series adds manual = control, > opening more use cases. >=20 > For example, setting CPUs aside for selected fair tasks at runtime = while > steering other fair tasks toward the remaining CPUs. Hi Yury, I've been trying to do this with crutches in user-space for a long time. = Thanks for implementing this in the kernel, and with a convenient user = interface. >=20 > A user can mark a CPU non-preferred and pin a workload to it. Fair = tasks > whose affinity includes preferred CPUs are steered away, while tasks > whose allowed CPUs contain no preferred CPU can still run there. The = CPU > stays online, task affinity is preserved, and the selection can be > reversed without rebooting: >=20 > # rmmod steal_governor > # echo 0 > /sys/devices/system/cpu/cpu3/preferred > # taskset -c 3 ./my_workload > # echo 1 > /sys/devices/system/cpu/cpu3/preferred My use-case (being a compiler optimization engineer) is to pin = benchmarks to specific cores, and stop the system from using those cores = even when the cores are idle. This prevents L1/L2 cache pollution and = makes performance numbers more stable. Thanks! -- Maxim Kuvyrkov Garden City Compilers