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Re: bumming cycles out of parse_identifier()...
On Mon, Sep 10, 2001 at 05:30:26PM -0700, Zack Weinberg wrote:
> On Mon, Sep 10, 2001 at 04:09:12PM -0700, Linus Torvalds wrote:
> > In article <20010910113642.D274@codesourcery.com> you write:
> > >
> > >This lets us keep the mmap performance win for the normal case where
> > >the file is properly ended. One potential problem is that accessing
> > >the last page of the file first may confuse the kernel into not doing
> > >read-ahead. I don't know enough kernel architecture to say for sure.
> > >(Richard? Linus?)
> >
> > The kernel will do read-ahead for mmap'ed areas only if the mapping has
> > ben marked sequential with madvise(). Some day in the future we _may_
> > become clever enough that we'll notice automatically (it's not that
> > hard). But not right now.
>
> Hmm. I should experiment with madvise and see if it makes a
> noticeable difference.
Obviously if you do wind up using madvise, you need to add appropriate
configure tests to check whether madvise and MADV_SEQUENTIAL are present.
--
Michael Meissner, Red Hat, Inc. (GCC group)
PMB 198, 174 Littleton Road #3, Westford, Massachusetts 01886, USA
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