[ccache] Compression on or off by default?

[Mike Frysinger]

On Tue, Mar 2, 2010 at 17:10, Joel Rosdahl wrote:
> Lars Gustäbel's compression patch (which will be incorporated in ccache 3.0)
> enables compression by default, and if you don't want compression you have to
> set CCACHE_NOCOMPRESS. I'm still a bit undecided about whether defaulting to
> compression is a good idea, though. Maybe we should be more conservative here
> and require CCACHE_COMPRESS to be set to enable compression instead? (Note that
> the question only is about the default behaviour when storing files in the
> cache -- ccache will still be able to read compressed and uncompressed files
> from the cache regardless of the CCACHE_(NO)COMPRESS setting.)
>
> The main argument I see for making compression opt-in is that hard-linking
> doesn't work for compressed files (where "doesn't work" means that ccache will
> fall back to copying), so if you would like to try out hard-linking, you must
> set both CCACHE_NOCOMPRESS and CCACHE_HARDLINK, and also build up the cache
> again. Or, if you currently have enabled hard-linking with ccache 2.4, you need
> to take the explicit action of disabling compression after an upgrade to get
> the previous behaviour.
>
> Another argument is maybe that disk space is cheap nowadays, and most people
> probably want to optimize for speed instead of disk space. On the other hand,
> the overhead of using compression is very small. In fact, I am unable to
> consistently measure any performance impact whatsoever. (Lars Gustäbel's own
> measurements can be found at <http://gustaebel.de/lars/ccache/>.) And, by
> compressing the cached files, more files will fit in the cache and also in the
> OS disk cache.
>
> Does anyone have an opinion to share about this?

make the default a ./configure option that defaults to off
-mike