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Date: Wed, 22 Jul 2015 12:28:34 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Christoph Lameter <cl@...ux.com> Cc: Andy Lutomirski <luto@...capital.net>, Chris Metcalf <cmetcalf@...hip.com>, Gilad Ben Yossef <giladb@...hip.com>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>, Frederic Weisbecker <fweisbec@...il.com>, Thomas Gleixner <tglx@...utronix.de>, Viresh Kumar <viresh.kumar@...aro.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, Linux API <linux-api@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v4 1/5] nohz_full: add support for "cpu_isolated" mode On Wed, Jul 22, 2015 at 08:57:45AM -0500, Christoph Lameter wrote: > On Tue, 21 Jul 2015, Paul E. McKenney wrote: > > > > > In the current version, there's also the vmstat_update() that > > > > may schedule delayed work and interrupt the core again > > > > shortly before realizing that there are no more counter updates > > > > happening, at which point it quiesces. Currently we handle > > > > this in cpu_isolated mode simply by spinning and waiting for > > > > the timer interrupts to complete. > > > > > > Perhaps we should fix that? > > > > Didn't Christoph Lameter fix this? Or is this an additional problem? > > Well the vmstat update must realize first that there are no outstanding > updates before switching itself off. So typically there is one extra tick. > But we could add another function that will simply fold the differential > immediately and turn the kworker task in the expectation that the > processor will stay quiet. Got it, thank you! Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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