From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 11 Jan 2010 19:29:01 GMT
Subject: Re: [PATCH] grep: do not do external grep on skip-worktree entries
Message-ID: <alpine.LFD.2.00.1001111124480.17145@localhost.localdomain>
In-Reply-To: <4c8ef71001111119p253170f8q37bcd3708d894a62@mail.gmail.com>



On Mon, 11 Jan 2010, Fredrik Kuivinen wrote:
> 
> Any ideas on how this can be explained?

Could it be a bad 'strstr()' implementation? 

Try a complex pattern ("qwerty.*as" finds the same line), and see if that 
too is slower than before. If that is faster than it used to be (with 
--no-ext-grep, of course), then it's strstr() that is badly implemented.

For me, on x86-64 (Fedora-12), strstr() seems to do pretty well. But it's 
easy to do a stupid implementation of strstr that does a 'strlen()' first, 
for example, and thus always traverses all data _twice_ etc. Depending on 
cache sizes etc, that can end up killing performance (or not mattering 
much at all..)

		Linus