Re: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest]

Rik van Riel
2003-02-10T13:16:44Z

On Mon, 10 Feb 2003, Andrea Arcangeli wrote:
> On Mon, Feb 10, 2003 at 10:45:59PM +1100, Nick Piggin wrote:
> > perspective it does nullify the need for readahead (though
> > it is obivously still needed for other reasons).
>
> I'm guessing that physically it may be needed from a head prospective
> too, I doubt it only has to do with the in-core overhead. Seeing it all
> before reaching the seek point might allow the disk to do smarter things

> NOTE: just to be sure, I'm not at all against anticpiatory scheduling,

Most disks seem to have a large cache, but with the cache unit
for most of the cache being one _track_ at a time.

This has the effect of the disk reading one track in at a time,
but only being able to cache a few of these tracks in its cache.

Anticipatory scheduling should reduce any thrashing of this disk
cache.

regards,

Rik
--
Bravely reimplemented by the knights who say "NIH".
http://www.surriel.com/ http://guru.conectiva.com/
Current spamtrap: october@surriel.com