Re: Poor performance of git describe in big repos

["Alex Bennée" <kernel-hacker@bennee.com>]

The repo is a fairly hairy one as it includes two historically
un-related but content related repos which I'm the process of
cherry-picking stuff across.

11:58 ajb@sloy/x86_64 [work.git] >git count-objects -v
count: 493
size: 4572
in-pack: 399307
packs: 1
size-pack: 1930755
prune-packable: 0
garbage: 0
size-garbage: 0

This was after a repack which did have slight negative effect on
performance. The pack file is:

13:27 ajb@sloy/x86_64 [work.git] >ls -lh ./.git/objects/pack/*
-r--r--r-- 1 ajb cvs  11M May 30 11:56
./.git/objects/pack/pack-a9ba133a6f25ffa74c3c407e09ab030f8745b201.idx
-r--r--r-- 1 ajb cvs 1.9G May 30 11:56
./.git/objects/pack/pack-a9ba133a6f25ffa74c3c407e09ab030f8745b201.pack

I ran perf on it and the top items in the report where:

 41.58%   git  libcrypto.so.1.0.0  [.] 0x6ae73
 33.96%   git  libz.so.1.2.3.4     [.] 0xe0ec
 10.39%   git  libz.so.1.2.3.4     [.] adler32
  2.03%   git  [kernel.kallsyms]   [k] clear_page_c

So I'm guessing it's spending a lot of non-cache efficient time
un-packing and processing the deltas?

--
Alex.

On 30 May 2013 12:48, John Keeping <john@keeping.me.uk> wrote:
> On Thu, May 30, 2013 at 11:38:32AM +0100, Alex Bennée wrote:
>> One factor might be the size of my repo (.git is around 2.4G). Could
>> this just be due to computational cost of searching through large
>> packs to walk the commit chain? Is there any way to make this easier
>> for git to do?
>
> What does "git count-objects -v" say for your repository?
>
> You may find that performance improves if you repack with "git gc
> --aggressive".



-- 
Alex, homepage: http://www.bennee.com/~alex/