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List:       kde-devel
Subject:    Re: ccache and distcc
From:       Lubos Lunak <l.lunak () suse ! cz>
Date:       2003-02-05 13:18:47
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On Wednesday 05 of February 2003 18:53, Pupeno wrote:
> On Wednesday 05 February 2003 06:36 am, Lubos Lunak wrote:
> > script is run from builddir). 'ccache' is simply ccache, picking the
> > right ccache repository based on current directory (I use different
> > ccache repositories for different CVS modules, so that they don't make
> > each other go away from the cache)
>
> What do you mean by "I use different ccache repositories for different CVS
> modules", won't they be automatically different since different CVS modules
> are diferent directories ?

 By ccache repository I meant the thing where CCACHE_DIR points to. If you 
e.g. compile kdelibs four times more often than kdebase, and use the same dir 
for caching both builds, it's possible the repeated builds of kdelibs will 
replace all kdebase cached files before you get to rebuilding kdebase again.

 In general, thinking that ccache will greatly speed up the compile is naive. 
In order to get cached result, the file has to be exactly the same after 
preprocessing, which means at most comments may change, including all files 
it #include-s.

 I'm now doing another rebuild of kdelibs, last one was on 24 Jan (12 days 
ago), the build is now in kdelibs/kio/kfile, and the hit ratio is less than 
10% (in other words, I got 22 hits and 233 misses, those hits maybe including 
some of those dummy.cpp files). Great, isn't it? If the previous build was 
done say 2 days ago, I'd get about 50%.

 Statistics reported by 'ccache -s' also (IIRC) include configure test 
programs in hits, so unless you make sure you don't use ccache when running 
configure (my scripts don't), you may get much better statistics than the 
reality is.

-- 
Lubos Lunak
KDE developer
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