linux-kernel - Re: [PATCH -mm 04/25] free swap space on swap-in/activation

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Message-ID: <28c262360806091930g70c96f59t627b4590ec59f729@mail.gmail.com>
Date:	Tue, 10 Jun 2008 11:30:46 +0900
From:	"MinChan Kim" <minchan.kim@...il.com>
To:	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
Cc:	"Rik van Riel" <riel@...hat.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, lee.schermerhorn@...com,
	"Hugh Dickins" <hugh@...itas.com>
Subject: Re: [PATCH -mm 04/25] free swap space on swap-in/activation

On Mon, Jun 9, 2008 at 10:38 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
> Hi Kim-san,
>
>>> - Can completely optimise the thing away if !CONFIG_SWAP.
>>
>> I think we can optimize more and more in case of if !CONFIG_SWAP.
>> If system are !CONFIG_SWAP, we can never  swap out anonymous pages.
>>
>> Don't we manage anonymous pages with list ?
>>
>> Such system don't need to insert anonymous pages into lru list when fault occur.
>> It is just needless overhead.
>>
>> Also, If we can't reclaim anonymous pages, don't we need anon rmap facility ?
>> I don't know well which subsystems used rmap.
>>
>> If pageout only use anonymous rmap for pageout,
>> we can remove anonymous rmapping code in case of !CONFIG_SWAP
>
> You are right.
> but I think rmap isn't bottle neck in embedded system.
> Why do you want remove that?

I think unnecessary code execution may increase power consumption and
cache footprint.
But I am not sure pageout just only one user in rmap.
If another subsystem (ex, xen, kvm) use rmap for managing memory, we
cannot remove rmap.



-- 
Kinds regards,
MinChan Kim
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