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[82.17.115.212]) by smtp.gmail.com with ESMTPSA id j39-20020a05600c1c2700b00393ee3deaf1sm1758378wms.9.2022.04.25.04.39.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Apr 2022 04:39:12 -0700 (PDT) Date: Mon, 25 Apr 2022 12:39:09 +0100 From: Aaron Tomlin To: Christoph Lameter Cc: frederic@kernel.org, mtosatti@redhat.com, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, pauld@redhat.com, neelx@redhat.com, oleksandr@natalenko.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v3] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too Message-ID: <20220425113909.u3smtztp66svlw4o@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: <20220422193647.3808657-1-atomlin@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2022-04-25 09:23 +0200, Christoph Lameter wrote: > On Fri, 22 Apr 2022, Aaron Tomlin wrote: > > > A customer provided some evidence which indicates that the idle tick was > > stopped; albeit, CPU-specific vmstat counters still remained populated. > > Thus one can only assume quiet_vmstat() was not invoked on return to the > > idle loop. > > Could we *always* fold the vmstat counters when entering idle mode? That > would make the logic less complicated. There is nothing else to do since > we are entering an idle state and if there are any counter deltas then we > have the time to process them. This may also decrease the time that > deltas exist significantly and an idle system will have accurate vmstat > counters. Hi Christoph, Thank you for your feedback. Yes, in the context of nohz, this patch should ensure it, if required, when the idle tick is to be stopped. Kind regards, -- Aaron Tomlin