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From: Christoph Lameter <cl@linux.com>
To: Shiraz Hashim <shiraz.linux.kernel@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	LKML <linux-kernel@vger.kernel.org>,
	hannes@cmpxchg.org, penguin-kernel@i-love.sakura.ne.jp
Subject: Re: vmstat: make vmstat_updater deferrable again and shut down on idle
Date: Thu, 21 Jan 2016 09:41:28 -0600 (CST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1601210940030.7063@east.gentwo.org> (raw)
In-Reply-To: <CAPub14_S6swU_SPzZjx_OwyWhPBzXsfaoQ4Xc4qAKTDbtmjPSA@mail.gmail.com>

On Thu, 21 Jan 2016, Shiraz Hashim wrote:

> > On idle we fold counters immediately. So there is no loss of accuracy.
>
> vmstat is scheduled by shepherd or by itself (conditionally). In case shepherd
> is deferred and vmstat doesn't schedule itself, then vmstat needs to wait
> for shepherd to be up and then schedule it. This may end up in delayed status
> update for all live cpus. Isn't it ?

The shepherd runs on a processor with an active tick and thus should do
its duty every 2 seconds as scheduled. Small milisecond range deferrals do
not matter much.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Lameter <cl@linux.com>
To: Shiraz Hashim <shiraz.linux.kernel@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	LKML <linux-kernel@vger.kernel.org>,
	hannes@cmpxchg.org, penguin-kernel@i-love.sakura.ne.jp
Subject: Re: vmstat: make vmstat_updater deferrable again and shut down on idle
Date: Thu, 21 Jan 2016 09:41:28 -0600 (CST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1601210940030.7063@east.gentwo.org> (raw)
In-Reply-To: <CAPub14_S6swU_SPzZjx_OwyWhPBzXsfaoQ4Xc4qAKTDbtmjPSA@mail.gmail.com>

On Thu, 21 Jan 2016, Shiraz Hashim wrote:

> > On idle we fold counters immediately. So there is no loss of accuracy.
>
> vmstat is scheduled by shepherd or by itself (conditionally). In case shepherd
> is deferred and vmstat doesn't schedule itself, then vmstat needs to wait
> for shepherd to be up and then schedule it. This may end up in delayed status
> update for all live cpus. Isn't it ?

The shepherd runs on a processor with an active tick and thus should do
its duty every 2 seconds as scheduled. Small milisecond range deferrals do
not matter much.

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  reply	other threads:[~2016-01-21 15:41 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-10 20:45 vmstat: make vmstat_updater deferrable again and shut down on idle Christoph Lameter
2015-12-10 20:45 ` Christoph Lameter
2015-12-10 23:31 ` Andrew Morton
2015-12-10 23:31   ` Andrew Morton
2015-12-11  1:41   ` Christoph Lameter
2015-12-11  1:41     ` Christoph Lameter
2015-12-14 18:32     ` Christoph Lameter
2015-12-14 18:32       ` Christoph Lameter
2016-01-20 13:52 ` Shiraz Hashim
2016-01-20 13:52   ` Shiraz Hashim
2016-01-20 15:12   ` Christoph Lameter
2016-01-20 15:12     ` Christoph Lameter
2016-01-21  6:24     ` Shiraz Hashim
2016-01-21  6:24       ` Shiraz Hashim
2016-01-21 15:41       ` Christoph Lameter [this message]
2016-01-21 15:41         ` Christoph Lameter

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