Messages in this thread | | | Date | Sat, 11 May 2002 16:24:34 +0200 | From | Jens Axboe <> | Subject | Re: O_DIRECT performance impact on 2.4.18 (was: Re: [PATCH] 2.5.14 IDE 56) |
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On Sat, May 11 2002, Roy Sigurd Karlsbakk wrote: > On Friday 10 May 2002 17:55, Linus Torvalds wrote: > > 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. > > Will the use of O_DIRECT affect disk elevatoring?
No, the I/O scheduler can't even tell whether it's being handed O_DIRECT buffers or not.
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