Re: best practices against long git rebase times?

From: Jeff King <peff@peff.net>
Date: Dec 7, 2015, 22:59 UTC
Message-ID: <20151207225957.GB3785@sigill.intra.peff.net>
In-Reply-To: <xmqqmvtllvfi.fsf@gitster.mtv.corp.google.com>

On Mon, Dec 07, 2015 at 02:56:33PM -0800, Junio C Hamano wrote:

Show 22 quoted lines

> Jeff King <peff@peff.net> writes:
> 
> > You're computing the patch against the parent for each of those 3000
> > commits (to get a hash of it to compare against the single hash on the
> > other side). Twelve minutes sounds long, but if you have a really
> > gigantic tree, it might not be unreasonable.
> >
> > You can also try compiling with "make XDL_FAST_HASH=" (i.e., setting
> > that option to the empty string). Last year I found there were some
> > pretty suboptimal corner cases, and you may be hitting one (we should
> > probably turn that option off by default; I got stuck on trying to find
> > a hash that would perform faster and never followed up[1].
> >
> > I doubt that is your problem, but it's possible).
> >
> > -Peff
> >
> > [1] http://thread.gmane.org/gmane.comp.version-control.git/261638
> 
> I vaguely recall having discussed caching the patch-ids somewhere so
> that this does not have to be done every time.  Would such an
> extension help here, I wonder?

I think you missed John's earlier response which gave several pointers to such caching schemes. :)

I used to run with patch-id-caching in my personal fork (I frequently use "git log --cherry-mark" to see what has made it upstream), but I haven't for a while. It did make a big difference in speed, but I never resolved the corner cases around cache invalidation.

-Peff