[libvirt-jenkins-ci PATCH 2/7] lcitool: Configure ccache using environment variables

[Daniel P. Berrangé]

On Mon, Mar 30, 2020 at 02:11:29PM +0200, Andrea Bolognani wrote:
> On Mon, 2020-03-30 at 12:45 +0100, Daniel P. Berrangé wrote:
> > On Fri, Mar 27, 2020 at 08:34:54PM +0100, Andrea Bolognani wrote:
> > > +export CCACHE_MAXSIZE="2G"
> > 
> > I was wondering what a good size for ccache would be. Is there any history
> > to why we picked 2G ?  Having it too big didn't really matter for the
> > Jenkins builders as it is kept local.  For GitLab the cache is downloaded
> > at start of the job off cloud cstorage. So we want it large enough to fit
> > a libvirt.git compile but small enough that outdated cruft gets purged
> > reasonably quickly, so we don't waste time in GitLab CI downloading GB's
> > of data that is no longer needed in the cache.
> > 
> > NB, this is NOT an objection to this patch, as 2GB is a pre-existing value
> > we used. Just want to know how we should consider tuning it in future.
> 
> I think we just scaled it down (from the default of 5 GiB) so that
> it would use most of the disk space that remained free in the VM's
> 15 GiB disk, while leaving some leeway to allow for repositories to
> grow. Nothing more scientific than that, I'm afraid.

Ok, I'll see if I can get some usage stats out of ccache for our CI jobs on
GitLab.

> Note that, for VMs, we're building not just libvirt but a bunch of
> other projects, so if we wanted to tweak it we'd have to take that
> into account as well and not size it for just libvirt itself.

True, but I imagine in terms of object size all the other projects probably
barely reach 5% of the main libvirt.git build size, so likely lost in the
noise.

Regards,
Daniel
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