Subject: Re: [PATCH 4/4] diffcore-pickaxe: optimize by trimming common initial and trailing parts

From: Junio C Hamano <[email-masked]>
Date: Thu, 26 Feb 2009 01:05:18 -0800

Junio C Hamano <[email-masked]> writes:

> With this optimization in place, the following query in the Linux kernel
> repository on my machine becomes about 40% faster:
>
> $ STRING='Ensure that the real time constraints are schedulable.'
> $ git log -S"$STRING" HEAD -- kernel/sched.c >/dev/null
>
> (Before the patch, best of 5 runs)
> 5.59user 0.15system 0:05.74elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (0major+39956minor)pagefaults 0swaps
>
> (After the patch, best of 5 runs)
> 3.04user 0.17system 0:03.23elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (0major+49697minor)pagefaults 0swaps
    
The file "kernel/sched.c" has roughly 900 changes applied to it, and over
its lifetime, it has grown from 5kB to 9kB in size.

I suspect a larger file might see a bigger performance boost.