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From Cliff Woolley <>
Subject Re: Remaining CPU bottlenecks in 2.0, revisited
Date Sat, 29 Sep 2001 22:15:28 GMT
On Sat, 29 Sep 2001, Justin Erenkrantz wrote:

> >                              % of total    cumulative %
> > rank function                 CPU time    of total CPU time
> > ---- ------------------       ----------  -----------------
> >  1. munmap                     18.16
> >  3. mmap                       11.96
> Most of these look related to OS things that we can't control.

Using mod_file_cache's MMapFile directive for frequently accessed files
that don't change often and that will get run through mod_include should
help quite a bit here.  (Or whatever the new mod_cache equivalent is if
there is one... I haven't kept up with recent developments on that front.)
That should virtually eliminate 30% of the CPU effort for those files
according to the numbers above, which is pretty impressive.  =-)

If anyone has ideas for extending these benefits into the mainline, I'd
love to hear them... for example, I still think that file_read needs to
store the apr_mmap_t that the file gets mapped into so that other
references to that file bucket (if any) that get read later don't have to
re-mmap the file.  This situation probably doesn't happen all THAT often
in current code, I would guess, but it's definitely possible, and every
little bit helps...


   Cliff Woolley
   Charlottesville, VA

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