Re: [PATCH 0/3] delta-island fixes
- Date: Thu, 22 Nov 2018 11:43:18 -0500
- From: Jeff King <peff@xxxxxxxx>
- Subject: Re: [PATCH 0/3] delta-island fixes
On Tue, Nov 20, 2018 at 10:06:57AM -0500, Derrick Stolee wrote:
> On 11/20/2018 4:44 AM, Jeff King wrote:
> > In cases like this I think it's often a good idea to have a perf test.
> > Those are expensive anyway, and we'd have the double benefit of
> > exercising the code and showing off the performance improvement. But the
> > delta-island code only makes sense on a very specialized repo: one where
> > you have multiple related but diverging histories. You could simulate
> > that by picking two branches in a repository, but the effect is going to
> > be miniscule.
> The changes in this series look correct. Too bad it is difficult to test.
> Perhaps we should add a performance test for the --delta-islands check that
> would trigger the failure (and maybe a clone afterwards). There are lots of
> freely available forks of git.git that present interesting fork structure.
> Here are three that would suffice to make this interesting:
> Of course, running it on a specific repo is up to the person running the
> perf suite.
I hadn't really considered the possibility of reconstructing a fork
network repository from public repos. It probably would be possible to
include a script which does so, although:
- I suspect it's going to be pretty expensive. We can use --reference
to reduce the size of subsequent clones, but just the repacks you
have to do to assemble the final shared repo can get pretty
- That's 3 forks. Our real-world case has over 4000. I'm not sure of
the size of the effects for smaller cases.
So in short, I think it's an interesting avenue to explore, but it might
turn out to be a dead-end. I'm not going to prioritize it right now, but
if somebody wants to play with it, I'd be happy to look over the