Messages in this thread | | | Date | Fri, 18 Dec 1998 21:56:00 +0100 (CET) | From | Rik van Riel <> | Subject | Re: mmap() is slower than read() on SCSI/IDE on 2.0 and 2.1 |
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On Sat, 19 Dec 1998, Chris Wedgwood wrote: > On Fri, Dec 18, 1998 at 09:05:26PM +0100, Rik van Riel wrote: > > > Some form of read-behind will give us optimal performance > > when the tiles are a lot smaller (say 1/4th) than the VM > > 'stripe size' we are using. > > Still wearning my "I'm not sure its always a good idea to second > guess the application hat" -- do we actually have any applications > that would make use of this?
- the database stuff you mentioned - a lot of tasks that access insanely large 'arrays', eg: - (astronomical) image viewers - matrix solvers - movie stuff when you watch an image sequence backwards (sometimes done during editing, skips because of a faulty read-ahead/behind algorithm are not tolerated) - probably some other multimedia stuff - ??
> > The actual disk I/O, of course, is still done in forward > > direction :) > > True... but if this is an issue, gobs of disk and RAID can help, > especially when it comes to random seeks.
Why spend money on gobs of disks when you can put a simple algorithm in the kernel that accomplishes the same effect?
regards,
Rik -- the flu hits, the flu hits, the flu hits -- MORE +-------------------------------------------------------------------+ | Linux memory management tour guide. H.H.vanRiel@phys.uu.nl | | Scouting Vries cubscout leader. http://www.phys.uu.nl/~riel/ | +-------------------------------------------------------------------+
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