Re: O_DIRECT performance impact on 2.4.18 (was: Re: [PATCH] 2.5.14 IDE 56)

From: Linus Torvalds (torvalds@transmeta.com)
Date: Fri May 10 2002 - 10:55:32 EST

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On Fri, 10 May 2002, Lincoln Dale wrote:
>
> so O_DIRECT in 2.4.18 still shows up as a 55% performance hit versus no
> O_DIRECT. anyone have any clues?

Yes.

O_DIRECT isn't doing any read-ahead.

For O_DIRECT to be a win, you need to make it asynchronous.

Linus

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