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[82.17.115.212]) by smtp.gmail.com with ESMTPSA id u11-20020a5d6acb000000b0022afedf3c87sm13662057wrw.105.2022.10.12.05.41.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Oct 2022 05:41:02 -0700 (PDT) Date: Wed, 12 Oct 2022 13:41:01 +0100 From: Aaron Tomlin To: Hillf Danton Cc: frederic@kernel.org, mtosatti@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, atomlin@atomlin.com Subject: Re: [PATCH v8 5/5] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too Message-ID: <20221012124101.zod6m2brlzpgx6nb@ava.usersys.com> X-PGP-Key: http://pgp.mit.edu/pks/lookup?search=atomlin%40redhat.com X-PGP-Fingerprint: 7906 84EB FA8A 9638 8D1E 6E9B E2DE 9658 19CC 77D6 References: <20220924152227.819815-1-atomlin@redhat.com> <20220925010511.1482-1-hdanton@sina.com> <20221003124435.1769-1-hdanton@sina.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221003124435.1769-1-hdanton@sina.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Given work canceled because per-CPU pages can be freed remotely from > housekeeping CPUs (see patch 3/5), what is added here is not needed. Hi Hillf, Firstly, apologies for the delay! The concern is to ensure CPU-specific vmstat counters are reset and folded into NUMA node and zone specific and global counters too before entering idle. It is necessary to invoke quiet_vmstat() on return to idle even if the scheduling-clock tick has been previously stopped. Please refer to the complete scenario I described again. If I understand correctly, indeed the remote drain/or free of zone CPU-specific pages can be initiated by a "housekeeping" CPU i.e. refresh_cpu_vm_stats(true) via a worker thread/or kworker, yet the actual free will only occur when the nohz_full CPU exits idle code and calls schedule_idle(). Kind regards, -- Aaron Tomlin