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Message-ID: <1338370380.20169.112.camel@ted>
From: Richard Purdie <richard.purdie@linuxfoundation.org>
To: Patches and discussions about the oe-core layer
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Date: Wed, 30 May 2012 10:33:00 +0100
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Subject: Re: [PATCH] ccache: Separate out into its own class
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On Tue, 2012-05-29 at 15:40 +0200, Enrico Scholz wrote:
> Richard Purdie
> <richard.purdie-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
> writes:
> 
> > Currently, ccache is used if it is present. When building from scratch
> > it gives no performance improvement
> 
> Here, I have a 10% cache hit ratio in a scratch build:
> 
> cache hit (direct)                  2841
> cache hit (preprocessed)            1370
> cache miss                         39957
> called for link                     3369
> called for preprocessing            3207
> multiple source files                  8
> compile failed                      2531
> preprocessor error                   432
> couldn't find the compiler           111
> bad compiler arguments               468
> unsupported source language          532
> autoconf compile/link               6613
> unsupported compiler option          132
> no input file                       2919
> files in cache                     94205
> cache size                           2.0 Gbytes
> max cache size                       3.0 Gbytes
> 

That's good data, thanks for sharing it. In any measurement I've made,
it doesn't seem to help the wall time for the build though :(

We're not removing the ability to use ccache, just changing the way its
enabled which all things considered I still think is a good move...

Cheers,

Richard