Write-ahead only makes sense when we can cluster the extra
I/O with the operation we were already going to do.
> I suppose a least-recently-used approach on the pages would have the
> highest payback.
LRU would be a very bad strategy since it wastes too much CPU
and it prevents us from writing the blocks to disk in such a
way that it makes swapin readahead efficient.
Remember that disk seek time is about 10 times as expensive
as transfer time. This means that we've got to optimize our
I/O patterns mainly for seek time -- transferring a few
blocks extra in one big I/O sweep isn't really costing us
anything. And once we do that, expensive schemes like LRU
really don't matter any more, do they?
regards,
Rik -- the flu hits, the flu hits, the flu hits -- MORE
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| 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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