Re: [RFC] mmaped copy too slow?

From: Paulo Marques
Date: Tue Jan 15 2008 - 07:46:44 EST


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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