Re: [PATCH] fast-export: ensure we traverse commits in topological order

On Wed, Feb 11, 2009 at 6:56 AM, Jeff King [off-list ref] wrote:

On Wed, Feb 11, 2009 at 10:48:18AM +0000, Mike Ralphson wrote:

quoted

quoted

On Tue, 10 Feb 2009, newren@gmail.com wrote:
fast-export will only list as parents those commits which have already
been traversed (making it appear as if merges have been squashed if not
all parents have been traversed).  To avoid this silent squashing of
merge commits, we request commits in topological order.

Any comparative timings? We don't need to rename this to 'git
reasonably-speedy-export'? 8-)

Hmm.

In git.git:

 $ time git fast-export --all --signed-tags=strip >/dev/null
 real    1m6.013s
 user    1m3.840s
 sys     0m2.140s

 $ time git fast-export --all --signed-tags=strip --topo-order >/dev/null
 real    0m49.018s
 user    0m47.987s
 sys     0m0.888s

I certainly didn't expect it to be _faster_.  More efficient use of the
delta cache, maybe?

Yeah, I also saw a speed-up, though the difference was less pronounced
-- 19.7 seconds versus 19.5 (that was the average for 5 runs, after
first doing a run that I ignored to make sure I was comparing
hot-cache to hot-cache).

I'm a little surprised why my numbers were so much lower than yours,
though.  I don't think of my hard drive and CPU as being all that
quick -- is this a difference in packing, by chance, with your
repository not having recently been repacked?