Messages in this thread | | | Subject | Re: mmap/write vs read/write supprise | Date | Fri, 11 Jul 1997 17:46:54 +0200 (MET DST) | From | (Rogier Wolff) |
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Eric.Schenk@dna.lth.se wrote: > > > mcculley@iag.net <mcculley@iag.net> 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.
ROger.
> > -- > Eric Schenk www: http://www.dna.lth.se/~erics > Dept. of Comp. Sci., Lund University email: Eric.Schenk@dna.lth.se > Box 118, S-221 00 LUND, Sweden fax: +46-46 13 10 21 ph: +46-46 222 96 38 > >
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