From: Joe Perches <joe@perches.com>
Date: Sun, 26 Jan 2014 21:10:52 GMT
Subject: git blame vs git log --follow performance
Message-ID: <1390770652.20150.25.camel@joe-AO722>

Hi.

Is there something that can be done about improving
git log --follow -- <file> performance to be nearly
equivalent speed to git blame -- <file> ?

The overall cpu time taken for these 2 commands that
track individual file history can be quite different.

	git log --follow -- <file>
and
	git blame -- <file>

It seems that there can be a couple orders of magnitude
delta in the overall time taken.

For instance (using the Linus' linux kernel git):

$ time git log --follow -- drivers/firmware/google/Kconfig > /dev/null

real	0m42.329s
user	0m40.984s
sys	0m0.792s

$ time git blame -- drivers/firmware/google/Kconfig > /dev/null

real	0m0.963s
user	0m0.860s
sys	0m0.096s

This particular file has never been renamed.

Looking at the output on screen, there does seem to
be 25+ seconds of cpu time consumed after the initial
(last shown) commit that introduces this file.

Perhaps adding a whole-file rename option to the
"git log" history simplification mechanism could
help?

Thoughts?