Re: [libvirt PATCH] ci: Reduce number of stages

On Wed, 2020-06-10 at 13:31 +0100, Daniel P. Berrangé wrote: > On Wed, Jun 10, 2020 at 01:14:51PM +0100, Daniel P. Berrangé wrote: > > On Wed, Jun 10, 2020 at 01:33:01PM +0200, Andrea Bolognani wrote: > > > Building artifacts in a separate pipeline stage also doesn't have any > > > advantages, and only delays further stages by a couple of minutes. > > > The only job that really makes sense in its own stage is the DCO > > > check, because it's extremely fast (less than 1 minute) and, if that > > > fails, we can avoid kicking off all other jobs. > > > > The advantage of using stages is that it makes it easy to see at a > > glance where the pipeline was failing. Ultimately you'll need to drill down to the actual failure, though, so the only situation in which it would really provide value is if for some reason *all* cross builds failed at once, which is not something that happens frequently enough to optimize for. > > > Reducing the number of stages results in significant speedups: > > > specifically, going from three stages to two stages reduces the > > > overall completion time for a full CI pipeline from ~45 minutes[1] > > > to ~30 minutes[2]. > > > > > > [1] https://gitlab.com/abologna/libvirt/-/pipelines/154751893 > > > [2] https://gitlab.com/abologna/libvirt/-/pipelines/154771173 > > > > I don't think this time comparison is showing a genuine difference. > > > > If we look at the original staged pipeline, every single individual > > job took much longer than every individual jobs in the simplified > > pipeline. I think the difference in job times accounts for most > > (possibly all) of the difference in the pipelines time. > > > > If we look at the history of libvirt pipelines: > > > > https://gitlab.com/libvirt/libvirt/pipelines > > > > the vast majority of the time we're completing in 30 minutes or > > less already. That was before introducing FreeBSD builds, which for whatever reason take a significantly longer time: the last couple of jobs both took 50+ minutes. Installing packages is very inefficient, it would seem.