Re: Bottlenecks in git merge

[Petr Baudis <pasky@suse.cz>]

Dear diary, on Wed, Feb 01, 2006 at 12:45:27AM CET, I got a letter
where Linus Torvalds <torvalds@osdl.org> said that...
> It would be interesting to see how big the "resolve 850 files" part is vs 
> the "check out 10k+ files" is.

See my other mail.

> In particular, if the "resolve 850 files" is a noticeable portion of it, 
> then the right thing to do may be to just re-write git-merge-one-file.sh 
> in C. Right now, almost _all_ of the expense of that thing is just the 
> shell interpreter startup. The actual actions it does are usually fairly 
> cheap.

Nope.

xpasky@machine[0:0]~/linux-2.6.git$ echo -e '#!/bin/sh\n/bin/true' >r && chmod a+x r
xpasky@machine[0:0]~/linux-2.6.git$ time git-merge-index -o ./r -a

real    0m3.827s
user    0m1.788s
sys     0m2.004s
xpasky@machine[0:0]~/linux-2.6.git$ time git-merge-index -o ~/git-pb/git-merge-one-file -a
[lots of "Removing"]

real    1m21.773s
user    0m30.806s
sys     0m13.248s

The costs are apparently in git-update-index, not in the shell.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
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