Re: Linux 2.4.2 fails to merge mmap areas, 700% slowdown.

Linus Torvalds (torvalds@transmeta.com)
23 Mar 2001 21:02:30 -0800


In article <vbawv9hyuj0.fsf@mozart.stat.wisc.edu>,
Kevin Buhr <buhr@stat.wisc.edu> wrote:
>
>The results speak for themselves:
>
> CVS gcc 3.0: Debian gcc 2.95.3: RedHat gcc 2.96:
>
> real 16m8.423s real 8m2.417s real 12m24.939s
> user 15m23.710s user 7m22.200s user 10m14.420s
> sys 0m48.730s sys 0m41.040s sys 2m13.910s
>maps: <250 lines <250 lines >3000 lines
>
>Obviously, the *real* problem is RedHat GCC 2.96. If Linus bothers to
>write this patch (he probably already has),

Check out 2.4.3-pre7, I'd be interested to hear what the system time is
for that one.

It does seem like gcc-2.96 is kind of special, but considering how easy
it is to merge anonymous memory (most of the changes were cosmetic ones
to get nice ordering to make the merge trivial without having to
allocate a vma that never gets used etc), it's certainly worth doing.

Linus
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