On Mon, 11 Jan 2010, Fredrik Kuivinen wrote:
>
> Another option is to use memmem instead. As we know the length of the
> buffer already it should be a slight improvement over strstr for
> everyone. memmem may cause some portability problems though as it is a
> GNU extension.
I'd almost prefer to just drop the strstr entirely.
It's not actually all *that* big a win, even on my machine. I get
- strstr:
real 0m0.309s
user 0m0.168s
sys 0m0.136s
- regexec:
real 0m0.410s
user 0m0.220s
sys 0m0.116s
so yeah, it's slower, but not by a huge degree. With strstr, "git grep"
actually beats the external grep for me, but I don't really care. It's
already way better than it used to be - and clearly strstr has a lot of
potential problems.
Sure memmem() might be better for you than strstr, but on the other hand,
it might easily be worse than strstr for others - and not just from a
portability standpoint. Is memmem() optimized to take advantage of SSE4.2?
I suspect it is not, exactly _because_ it's a GNU extension, so Intel
hasn't published optimized sample code for people to use.
So I would argue against even bothering to try memmem. Especially since in
your case, regexec() is apparently faster than memmem _anyway_. I expect
that it is for me too, but I'm too lazy to check.
Linus
--
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html