[ccache] explanation of ccache stats
Stéphane Charette
stephanecharette at gmail.com
Thu Mar 17 20:29:41 UTC 2016
>
>
> 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
>
>
This started out as a plugin just for myself. I needed to come up with a
way to find the ccache directory without hard-coding my username into the
plugin.
If there is a better way for root to find all the ccache directories
without hard-coding a value, please let me know! This was the best I could
come up with.
In an enterprise setting, this will cause a lot of thrashing
> only to come up with nothing since ccache isn't stored there.
>
Correct, if the ccache directories are not stored in the user's home
directories, then that line would have to be changed. I guess this limits
the plugin to people like myself using ccache on a system with "normal"
configuration.
> 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.
>
Correct, I was just curious to see how "effective" ccache was in my
projects, in terms of hits versus misses. (I'm averaging 75%.) Also note
that the only stats I know about (since I've never dug into the ccache
source code) is the output of ccache --show-stats. Are there other stats
not reported in --show-stats? If so, where are they stored?
Otherwise, it is looking good! Especially like the "effectiveness".
> Not sure if 1-min or 5-min is best, guess it depends on volume...
>
Munin runs every 5 minutes. That I don't get to define. But unless the
ccache stats are being reset back down to zero more often than once every 5
minutes, this shouldn't be a problem. (
http://munin-monitoring.org/wiki/faq#Q:CanIrunmuninatdifferenttimeintervalsthanthedefault
)
Stéphane
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