linux-kernel - Re: [RFC 2/3] vmscan hook

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Message-ID: <4F16D46D.5080000@redhat.com>
Date:	Wed, 18 Jan 2012 09:17:17 -0500
From:	Rik van Riel <riel@...hat.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Minchan Kim <minchan@...nel.org>, linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, leonid.moiseichuk@...ia.com,
	penberg@...nel.org, mel@....ul.ie, rientjes@...gle.com,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ronen Hod <rhod@...hat.com>
Subject: Re: [RFC 2/3] vmscan hook

On 01/17/2012 07:18 PM, KAMEZAWA Hiroyuki wrote:
> On Wed, 18 Jan 2012 08:08:01 +0900
> Minchan Kim<minchan@...nel.org>  wrote:
>
>>>>> 2. can't we measure page-in/page-out distance by recording something ?
>>>>
>>>> I can't understand your point. What's relation does it with swapout prevent?
>>>>
>>>
>>> If distance between pageout ->  pagein is short, it means thrashing.
>>> For example, recoding the timestamp when the page(mapping, index) was
>>> paged-out, and check it at page-in.
>>
>> Our goal is prevent swapout. When we found thrashing, it's too late.
>
> If you want to prevent swap-out, don't swapon any. That's all.
> Then, you can check the number of FILE_CACHE and have threshold.

I think you are getting hung up on a word here.

As I understand it, the goal is to push out the point where
we start doing heavier swap IO, allowing us to overcommit
memory more heavily before things start really slowing down.

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