Re: q: faster way to integrate/merge lots of topic branches?

From: Pierre Habouzit <madcoder@artemis.madism.org>
Date: Jul 23, 2008, 19:09 UTC
Message-ID: <20080723190920.GG20614@artemis.madism.org>
In-Reply-To: <alpine.LFD.1.10.0807231027030.4754@woody.linux-foundation.org>

On Wed, Jul 23, 2008 at 05:59:01PM +0000, Linus Torvalds wrote:

Show 8 quoted lines

> In fact, the two top entries in a profile look roughly like:
> 
> 	102161   70.2727  libz.so.1.2.3            libz.so.1.2.3            (no symbols)
> 	7685      5.2862  git                      git                      find_pack_entry_one
> 	...
> 
> ie 70% of the time is just purely unpacking the data, and another 5% is 
> just finding it. We could perhaps improve on it, but not a whole lot.

  Well there is an easy way though, that could reduce that: using
adaptative compression. I proposed a patch once upon a time, that set
the compression strengh to 0 for "small" objects with a configurable
cut-off. If you do that, most trees, commits messages and so on aren't
compressed, and it will reduce (with IIRC a 5-liner) this time quite
dramatically.

  I could maybe resurect it to see if for people that do the kind of
things Ingo does it helps. By setting the cut-off at 1k, I had packs
being less than 1% bigger IIRC. I'll try to find it again and run your
tests with it to see how much it helps.

  [ Of course, it doesn't invalidate the rest of your mail about being
    more clever with git-merge, but still, we could reduce this 70% of
    zlib time quite a lot with that ]

-- 
·O·  Pierre Habouzit
··O                                                madcoder@debian.org
OOO                                                http://www.madism.org