Re: [PATCH] grep: do not do external grep on skip-worktree entries

[Linus Torvalds <torvalds@linux-foundation.org>]

On Mon, 4 Jan 2010, Linus Torvalds wrote:
> 
>  - external grep:
> 
> 	[torvalds@nehalem linux]$ time git grep qwerty
> 	...
> 	real	0m0.412s
> 	user	0m0.196s
> 	sys	0m0.132s
> 
>  - NO_EXTERNAL_GREP:
> 
> 	[torvalds@nehalem linux]$ time ~/git/git grep qwerty
> 	...
> 	real	0m1.006s
> 	user	0m0.900s
> 	sys	0m0.096s
> 
> so that's not even close.

Side note: at least for me, if we did some auto-parallelization, the 
internal grep would make up for all its other suckiness. Do four or eight 
greps in parallel, and buffer the results (you still need to show them in 
the right order).

That might be an acceptable way to "fix" it. Developers pretty much all 
have at least two cores these days, some of us have four+HT. We use 
threads in other places, maybe this could be one more of them.

(Start 'n' threads, do an initial per-thread regex and 'regcomp()' to make 
it thread-safer, and the only interesting issue would be serializing the 
output. Whenever you get a result, you'd need to make sure that all files 
before have been completed, but you could do that all under a specific 
lock that protects completion information).

		Linus