Re: best practices against long git rebase times?

From: Christian Couder <christian.couder@gmail.com>
Date: Dec 8, 2015, 17:45 UTC
Message-ID: <CAP8UFD3fmNSwSBLifWEsCBCSvY74Wh+9auvqyup4mN4Lx1Pf7g@mail.gmail.com>
In-Reply-To: <20151207225957.GB3785@sigill.intra.peff.net>

On Mon, Dec 7, 2015 at 11:59 PM, Jeff King <peff@peff.net> wrote:

Show 27 quoted lines

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

Yeah, he also gave very interesting performance numbers. Thanks John!

> 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.

I will see if I can work on that after I am done with untracked cache...