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Fri, 02 Oct 2026 06:12:02 -0700 (PDT) From: Qiliang Yuan Date: Fri, 02 Oct 2026 21:10:31 +0800 Subject: [PATCH v5 11/12] docs: cgroup-v2: Document kernel-noise isolation via isolated partitions 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: 7bit Message-Id: <20261002-wujing-dhm-v5-11-78a6996d87ad@gmail.com> References: <20261002-wujing-dhm-v5-0-78a6996d87ad@gmail.com> In-Reply-To: <20261002-wujing-dhm-v5-0-78a6996d87ad@gmail.com> To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Anna-Maria Behnsen , Tejun Heo , Jonathan Corbet , Shuah Khan , Shuah Khan , Thomas Gleixner Cc: Waiman Long , linux-kernel@vger.kernel.org, rcu@vger.kernel.org, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Qiliang Yuan X-Mailer: b4 0.13.0 Document that creating a cpuset isolated partition updates the kernel-noise housekeeping masks (HK_TYPE_KERNEL_NOISE and HK_TYPE_MANAGED_IRQ) in addition to the sched-domain mask, and that destroying it restores the boot configuration. No boot-time kernel parameters such as nohz_full= or rcu_nocbs= are required; writing "isolated" to cpuset.cpus.partition is the only mechanism needed. Signed-off-by: Qiliang Yuan --- Documentation/admin-guide/cgroup-v2.rst | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 86a2a0099178e..611c6f7ca4efe 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -2784,6 +2784,23 @@ Cpuset Interface Files kernel boot command line option. If those CPUs are to be put into a partition, they have to be used in an isolated partition. + When an isolated partition is created or destroyed, the kernel + automatically drives runtime updates of the housekeeping masks + for kernel-noise types (nohz_full, RCU NOCB, managed IRQ + interrupts). This extends isolation beyond scheduler domains: + the tick is stopped on isolated CPUs, RCU callbacks are + offloaded to housekeeping cores, and managed interrupts are + migrated away. No boot-time kernel parameters such as + ``nohz_full=`` or ``rcu_nocbs=`` are required; writing + ``isolated`` to ``cpuset.cpus.partition`` is the only mechanism + needed. No additional cgroupfs files are required. + + CPUs with hotplug disabled (typically the boot CPU, CPU 0, on + x86-64) cannot be cycled offline for kernel-noise isolation. + The kernel emits a one-time warning and keeps those CPUs in + the tick and RCU-NOCB housekeeping set, even when they appear + in an isolated partition. + Device controller ----------------- -- 2.43.0