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SubjectRe: fadvise syscall?
At 19:20 17/03/02, Joel Becker wrote:
>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.

Oh absolutely. For mp3s, dvds, etc. Note I wrote O_SEQUENTIAL... Perhaps I
didn't emphasize it enough. In multimedia applications you very well know
in advance what you want so you can specify it at open(2) time.

Best regards,


"I've not lost my mind. It's backed up on tape somewhere." - Unknown
Anton Altaparmakov <aia21 at> (replace at with @)
Linux NTFS Maintainer / WWW:
ICQ: 8561279 / WWW:

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