Re: [StGit PATCH 0/2] push optimizations

On 2008-07-07 22:12:26 +0100, Catalin Marinas wrote:

2008/7/2 Karl Hasselström [off-list ref]:

quoted

Here's the git-apply call you asked for. You were right: it was a
huge speed-up.

I know, I've been through this couple of years ago :-)

:-P

quoted

I set up a benchmark to test it:

 * 32 directories, each containing 32 subdirectories, each
   containing 32 small (and different) files.

Can you try with a Linux kernel like the -mm tree? You get normally
sized patches which might show a difference with the patch log. You
can clone the for-akpm branch on git://linux-arm.org/linux-2.6 and
just uncommit ~300 patches.

Sure, I'll do that. (But one of the reasons I chose a fully synthetic
benchmark is that I wanted to start a performance suite similar to our
test suite, and we want such a thing to be repeatable but not too
large. (That said, operating on points of the kernel history that are
fixed should do the trick as well. I'll try to find such points -- a
long string of -mm patches somewhere in the history maybe?))

quoted

 * I set all this up with a python script feeding fast-import. A
   huge time-saver!

What is fast-import?

man git-fast-import

I'll try to clean up and publish the script I used.

quoted

 * Pop patches, git-reset to upstream, then goto top patch. This
   makes sure that we use the new infrastructure to push, and that
   we get one file-level conflict in each patch.

Before the first patch, the "goto" command took 4:27 minutes,
wall-clock time. After the first patch, it took 1:31. After the
second, 0:48; one second or so slower than the stable branch
(which does not have a patch stack log).

One second is just noise and depends on how warm the caches are. You
could run a few times consecutively and discard the first result but
we don't need to be that accurate.

I did run a few times, and it did indeed fluctuate some -- but I'm
pretty sure there was a measurable slowdown. Though I agree that it's
close enough that it doesn't really make a difference.

-- 
Karl Hasselström, kha@treskal.com
      www.treskal.com/kalle