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[82.17.115.212]) by smtp.gmail.com with ESMTPSA id t2-20020a1c4602000000b003917d43d339sm11918988wma.4.2022.04.25.07.17.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Apr 2022 07:17:19 -0700 (PDT) Date: Mon, 25 Apr 2022 15:17:17 +0100 From: Aaron Tomlin To: Peter Zijlstra Cc: Christoph Lameter , frederic@kernel.org, mtosatti@redhat.com, tglx@linutronix.de, mingo@kernel.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: <20220425141717.vw2jfnn3zp6c5ib2@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> <20220425113909.u3smtztp66svlw4o@ava.usersys.com> <20220425132700.GK2731@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220425132700.GK2731@worktop.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2022-04-25 15:27 +0200, Peter Zijlstra wrote: > On Mon, Apr 25, 2022 at 02:09:06PM +0200, Christoph Lameter wrote: > > On Mon, 25 Apr 2022, Aaron Tomlin wrote: > > > > > Yes, in the context of nohz, this patch should ensure it, if required, when > > > the idle tick is to be stopped. > > > > What I said was that it is generally useful. Even in the non NOHZ case. > > > > Folding the vmstat diffs *always* when entering idle prevents unnecessary > > wakeups and processing in the future and also provides more accurate > > counters for the VM allowing better decision to be made on reclaim. > > I'm thinking you're going to find a ton of regressions if you try it > though; some workloads go idle *very* shortly, doing all this accounting > is going to be counter-productive. Hi Peter, Christoph, Indeed. Which was why I decided, initially, against the general-purpose case/or approach. Personally, I would prefer to keep this somewhat restrictive to nohz. Kind regards, -- Aaron Tomlin