Re: Debugging git-commit slowness on a large repo

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Dec 7, 2011, 02:08 UTC
Message-ID: <CACsJy8Dbd+v+8FzvQS9a4C8DQSxQGgqQNGaLhL1cHv-yMnaCJQ@mail.gmail.com>
In-Reply-To: <CB04005C.2C669%joshua.redstone@fb.com>

On Wed, Dec 7, 2011 at 8:48 AM, Joshua Redstone <joshua.redstone@fb.com> wrote:

> I tried doing a 'git read-tree HEAD' before each 'git add ; git commit'
> iteration, and the time for git-commit jumped from about 1 second to about
> 8 seconds.  That is a pretty dramatic slowdown.  Any idea why?  I wonder
> if that's related to the overall commit slowness.

How big is your working directory? "git ls-files | wc -l" should show it. Try "git read-tree HEAD; git add; git write-tree" and see if the write-tree part takes as much time as commit. write-tree is mainly about cache-tree generation.

> @Carlos and/or @Junio, can you point me at any docs/code to understand
> what a tree-cache is and how it differs from the index?  I did a google
> search for [git tree-cache index], but nothing popped out.

Have a look at Documentation/technical/index-format.txt. Cache tree extension is near the end.

-- 
Duy