> > > I thought I'd get higher I/O throughput if I gave the application mmap()
> > > access to the
> > > I/O buffers. Throughput was down by 50% on a 166MHz Pentium and by 30% on
> > > a 1.2GHz Duron. I don't do copy_to/from_user() now but throughput is now
> > > lower.
> > > What is going on?
> > IIRC mmap doesn't do read-ahead like normal reads. bear in mind that
> > using mmap alters the pagetables so it depends on the access pattern.
> Perhaps some kind of prefetching would help. Read a word from next page?
Perhaps madvise would be a better choice. (It should be if
madvise is reasonably implemented.)
Kasper Dupont -- der bruger for meget tid p? usenet.