linux-kernel - Re: Over-eager swapping

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Message-ID: <4F980D32.8020309@redhat.com>
Date:	Wed, 25 Apr 2012 10:41:54 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Richard Davies <richard@...chsys.com>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Minchan Kim <minchan.kim@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Chris Webb <chris@...chsys.com>
Subject: Re: Over-eager swapping

On 04/23/2012 05:27 AM, Richard Davies wrote:

> The rrd graphs at http://imgur.com/a/Fklxr show a typical incident.
>
> We estimate memory used from /proc/meminfo as:
>
>    = MemTotal - MemFree - Buffers + SwapTotal - SwapFree
>
> The first rrd shows memory used increasing as a VM starts, but not getting
> near the 64GB of physical RAM.
>
> The second rrd shows the heavy swapping this VM start caused.
>
> The third rrd shows a multi-gigabyte jump in swap used = SwapTotal - SwapFree
>
> The fourth rrd shows the large load spike (from 1 to 15) caused by this swap
> storm.

These are exactly the kind of swap storms that led me
make the VM tweaks that got merged into 3.4-rc :)

See these commits:

fe2c2a106663130a5ab45cb0e3414b52df2fff0c
7be62de99adcab4449d416977b4274985c5fe023
aff622495c9a0b56148192e53bdec539f5e147f2
1480de0340a8d5f094b74d7c4b902456c9a06903
496b919b3bdd957d4b1727df79bfa3751bced1c1
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