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Mon, 30 Mar 2026 04:44:16 -0700 (PDT) Received: from localhost.localdomain ([74.48.213.230]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-12ab97ca83bsm7083511c88.2.2026.03.30.04.44.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); 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> MIME-Version: 1.0 Content-Type: text/plain; charset=yes Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A746040002 X-Stat-Signature: 4m4x94e9zzcbyywhwsxcje4bgtayb89p X-HE-Tag: 1774871057-734595 X-HE-Meta: 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 TsW9tO1y 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.