linux-kernel - Re: [RFC] mmaped copy too slow?

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Message-ID: <478CAB25.30300@grupopie.com>
Date:	Tue, 15 Jan 2008 12:46:29 +0000
From:	Paulo Marques <pmarques@...popie.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC] mmaped copy too slow?

KOSAKI Motohiro wrote:
> Hi
> 
> at one point, I found the large file copy speed was different depending on
> the copy method.
> 
> I compared below method
>  - read(2) and write(2).
>  - mmap(2) x2 and memcpy.
>  - mmap(2) and write(2).
> 
> in addition, effect of fadvice(2) and madvice(2) is checked.
> 
> to a strange thing, 
>    - most faster method is read + write + fadvice.
>    - worst method is mmap + memcpy.

One thing you could also try is to pass MAP_POPULATE to mmap so that the 
page tables are filled in at the time of the mmap, avoiding a lot of 
page faults later.

Just my 2 cents,

-- 
Paulo Marques - www.grupopie.com

"All I ask is a chance to prove that money can't make me happy."
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