Re: mmap/write vs read/write supprise

Rogier Wolff (
Fri, 11 Jul 1997 17:46:54 +0200 (MET DST) wrote:
> <> writes:
> >If we had madvise, the responsibility for determining the access
> >pattern could be put on the application. We could still use a better
> >default access pattern for mmap'd pages, though. Is the VM code
> >sophisticated enough yet to take advantage of an madvise syscall?
> Another approach to this would be to use a predictive algorithm
> to determine which pages to prefetch. There was a neat article
> on doing this in JACM recently. The idea is to use the core of
> a good compression algorithm as the predictor. Apparently
> this can be proved to be within a constant of the optimal
> prefect strategy (i.e. the one that knows all future
> fetches in advance). I don't know off hand what the real
> performance of this would be like for kernel VM, but
> someone ambitious with a lot of time on their hands
> may want to play :)

Compression algorithm (compress, gzip) work by assigning "short
bitstreams" to "strings that we've recently seen".

I don't see how this can be adapted to predicting access patterns.


> --
> Eric Schenk www:
> Dept. of Comp. Sci., Lund University email:
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