Re: git blame vs git log --follow performance

From: Duy Nguyen <pclouds@gmail.com>
Date: Jan 27, 2014, 01:33 UTC
Message-ID: <CACsJy8B4dkjae3tL+_JvD63HCoi_-nNWYGvT3xRTqi8UpYX95g@mail.gmail.com>
In-Reply-To: <1390770652.20150.25.camel@joe-AO722>

On Mon, Jan 27, 2014 at 4:10 AM, Joe Perches <joe@perches.com> wrote:

Show 14 quoted lines

> 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
>

It's not fair to compare blame and log. If you compare, compare it to non follow version

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

real 0m35.552s user 0m35.120s sys 0m0.383s

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

real 0m4.366s user 0m4.215s sys 0m0.144s

Although because we need to detect rename, we can't really filter to one path. So the base line is more like

$ time git log > /dev/null

real 0m29.338s user 0m28.485s sys 0m0.813s

with rename detection taking some more time.

Show 5 quoted lines

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

I tested a version with rename detection logic removed. It did not change the timing significantly. To improve --follow I think we need to do something about path filtering.

-- 
Duy