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Mon, 30 Mar 2026 04:44:16 -0700 (PDT) From: Qiliang Yuan To: peterz@infradead.org Cc: longman@redhat.com, cgroups@vger.kernel.org, akpm@linux-foundation.org, anna-maria@linutronix.de, boqun.feng@gmail.com, bsegall@google.com, dietmar.eggemann@arm.com, frederic@kernel.org, hannes@cmpxchg.org, jackmanb@google.com, jiangshanlai@gmail.com, joelagnelf@nvidia.com, josh@joshtriplett.org, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, mathieu.desnoyers@efficios.com, mgorman@suse.de, mhocko@suse.com, mingo@kernel.org, mingo@redhat.com, neeraj.upadhyay@kernel.org, paulmck@kernel.org, qiang.zhang@linux.dev, rcu@vger.kernel.org, realwujing@gmail.com, rostedt@goodmis.org, shuah@kernel.org, surenb@google.com, tglx@kernel.org, tj@kernel.org, urezki@gmail.com, vbabka@suse.cz, vincent.guittot@linaro.org, vschneid@redhat.com, ziy@nvidia.com Subject: Re: [PATCH 01/15] sched/isolation: Support dynamic allocation for housekeeping masks Date: Mon, 30 Mar 2026 19:43:21 +0800 Message-ID: <20260330114348.102265-1-realwujing@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260325135707.GZ3738786@noisy.programming.kicks-ass.net> References: <20260325135707.GZ3738786@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=yes Content-Transfer-Encoding: 8bit Hi Peter, On Wed, Mar 25, 2026 at 02:57:07PM +0100, Peter Zijlstra wrote: > I think I asked this a while ago; why do we have more than one mask? > What is the actual purpose of being able to separate RCU from Timers? That's a fair point. For the vast majority of use cases (like NOHZ_FULL), these masks are indeed identical and should be updated as a single unit. The original motivation for separation was to allow extreme fine-tuning in HFT environments—for example, offloading RCU callbacks to keep a core mostly clean but allowing pinned timers for specific localized telemetry/monitoring. However, I acknowledge this adds significant complexity. In V13, I will unify these into a single "Global Housekeeping Mask" by default to simplify the configuration space, while keeping the underlying notifier infrastructure flexible enough for future specialized needs.