Re: Debugging git-commit slowness on a large repo

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 20, 2011, 01:21 UTC
Message-ID: <7vehw0kphc.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CB1518AB.2D649%joshua.redstone@fb.com>

Joshua Redstone <joshua.redstone@fb.com> writes:

Show 11 quoted lines

> I've managed to speed up git-commit on large repos by 4x by removing some
> safeguards that caused git to stat every file in the repo on commits that
> touch a small number of files.  The diff, for illustrative purposes only,
> is at:
>
>     https://gist.github.com/1499621
>
>
> With a repo with 1 million files (but few commits), the diff drops the
> commit time down from 7.3 seconds to 1.8 seconds, a 75% decrease. The
> optimizations are:

I do not know if these kind of changes are called "optimizations" or merely making the command record a random tree object that may have some resemblance to what you wanted to commit but is subtly incorrect. I didn't fetch your safety removal, though.

Wouldn't you get a similar speed-up without being unsafe if you simply ran "git commit" without any parameter (i.e. write out the current index as a tree and make a commit), combined with "--no-status" and perhaps "-q" to avoid running the comparison between the resulting commit and the working tree state after the commit?