[ccache] explanation of ccache stats

[Anders Björklund]

Stéphane Charette wrote:

>> I created a new web page with some example graphs from the ccache plugins
>> in case anyone wants to see what it looks like:
>> https://www.ccoderun.ca/ccache-munin/
>
> ...and I should have mentioned, if anyone has more ideas on additional
> graphs I can extract from ccache information, let me know and I'll create
> the necessary plugins.

Hmm, I looked at the code a bit and I don't think this will fly:

find /home -maxdepth 3 -type f -name ccache.conf | sort

In an enterprise setting, this will cause a lot of thrashing
only to come up with nothing since ccache isn't stored there.
One would probably have to specify the $CCACHE_DIR in config
(and it is possible to share one ccache between several users)


This is reasonable, but misses those things not being reported:

ccache_total=$((ccache_hit + ccache_miss))

That is, if ccache fails for some other reason you won't see it.
Maybe those _are_ uninteresting, but it could be nice to know ?
If reporting the total too, then the "unknowns" can be plotted.
But reporting _all_ the failure reasons makes too many counters.


Otherwise, it is looking good! Especially like the "effectiveness".
Not sure if 1-min or 5-min is best, guess it depends on volume...

Should clean ours up and release it too. It is written in Python.
Maybe one could read stats, instead of forking `ccache -s` ? Nah.

i.e. libccache or something

/Anders