linux-kernel - Re: vmstat: make vmstat_updater deferrable again and shut down on idle

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Message-ID: <alpine.DEB.2.20.1601200910480.21388@east.gentwo.org>
Date:	Wed, 20 Jan 2016 09:12:52 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Shiraz Hashim <shiraz.linux.kernel@...il.com>
cc:	Michal Hocko <mhocko@...nel.org>, akpm@...ux-foundation.org,
	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	hannes@...xchg.org, penguin-kernel@...ove.sakura.ne.jp
Subject: Re: vmstat: make vmstat_updater deferrable again and shut down on
 idle

On Wed, 20 Jan 2016, Shiraz Hashim wrote:

> The patch makes vmstat_shepherd deferable which if is quiesed
> would not schedule vmstat update on other cpus. Wouldn't this
> aggravate the problem of vmstat for rest cpus not gettng updated.

Its only "deferred" in order to make it at the next tick and not cause an
extra event. This means that vmstat will run periodically from tick
processing. It merely causes a synching so that we have one interruption
that does both.

On idle we fold counters immediately. So there is no loss of accuracy.