Re: fadvise syscall?

Joel Becker (jlbec@evilplan.org)
Sun, 17 Mar 2002 19:20:28 +0000

On Sun, Mar 17, 2002 at 01:41:37PM +0000, Anton Altaparmakov wrote:
> When you want large data streaming, i.e. you start getting worried about
> memory pressure, then you want open(2) + O_DIRECT. No caching done. Perfect
> for large data streams and we have that already. I agree that you may want
> some form of asynchronous read ahead with passed pages being dropped from
> the cache but that could be just a open(2) + O_SEQUENTIAL (doesn't exist yet).

O_DIRECT isn't the right thing for large streaming. You want
readahead and dropbehind. O_DIRECT takes substantial penalties for its
lack of copy/cacheing. This works fine in certain circumstances
(applications that keep their own caching), but for something like a
video or mp3, you'll win with working dropbehind easily.

Joel

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			jlbec@evilplan.org
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