From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Shawn O. Pearce" <spearce@spearce.org>
Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
Junio C Hamano <junkio@cox.net>, Nicolas Pitre <nico@cam.org>,
Morten Welinder <mwelinder@gmail.com>,
Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH 3/2] Avoid unnecessary strlen() calls
Date: Mon, 19 Mar 2007 21:11:08 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0703192052380.6730@woody.linux-foundation.org> (raw)
In-Reply-To: <20070320034020.GB29145@spearce.org>
On Mon, 19 Mar 2007, Shawn O. Pearce wrote:
>
> DrNick suggested on #git to try flipping the isspace test around.
> This is a smaller change and generated the same ~3.60 seconds run
> as Dscho's patch. I like DrNick's version better. ;-)
For me, the result seems to be in the noise.
It may be due to running on Core 2. It's not very sensitive to
micro-optimizations like this. It definitely makes sense to test the
*stable* test first, since that will help branch prediction (the
"isspace()" test is *not* very predictable), so I don't disagree with the
patch, but I suspect it depends a lot on the microarchitecture just how
much it matters.
Do you perhaps have a P4? It has a very bad branch mispredict penalty, so
putting the predictable branch first could explain the big difference you
see..
Dscho's bigger patch probably helps more on an in-order architecture, and
should be equally good on a P4 (or Opteron). On Core 2, neither of the
patches seem to make a huge difference.
Linus
next prev parent reply other threads:[~2007-03-20 4:11 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-16 1:04 cleaner/better zlib sources? Linus Torvalds
2007-03-16 1:10 ` Shawn O. Pearce
2007-03-16 1:11 ` Jeff Garzik
2007-03-16 1:14 ` Matt Mackall
2007-03-16 1:46 ` Linus Torvalds
2007-03-16 1:54 ` Linus Torvalds
2007-03-16 2:43 ` Davide Libenzi
2007-03-16 2:56 ` Linus Torvalds
2007-03-16 3:16 ` Davide Libenzi
2007-03-16 16:21 ` Linus Torvalds
2007-03-16 16:24 ` Davide Libenzi
2007-03-16 16:35 ` Linus Torvalds
2007-03-16 19:21 ` Davide Libenzi
2007-03-17 0:01 ` Linus Torvalds
2007-03-17 1:11 ` Linus Torvalds
2007-03-17 3:28 ` Nicolas Pitre
2007-03-17 5:19 ` Shawn O. Pearce
2007-03-17 17:55 ` Linus Torvalds
2007-03-17 19:40 ` Linus Torvalds
2007-03-17 19:42 ` [PATCH 1/2] Make trivial wrapper functions around delta base generation and freeing Linus Torvalds
2007-03-17 19:44 ` [PATCH 2/2] Implement a simple delta_base cache Linus Torvalds
2007-03-17 21:45 ` Linus Torvalds
2007-03-17 22:37 ` Junio C Hamano
2007-03-17 23:09 ` Linus Torvalds
2007-03-17 23:54 ` Linus Torvalds
2007-03-18 1:13 ` Nicolas Pitre
2007-03-18 7:47 ` Junio C Hamano
2007-03-17 23:12 ` Junio C Hamano
2007-03-17 23:24 ` Linus Torvalds
2007-03-17 23:52 ` Jon Smirl
2007-03-18 1:14 ` Morten Welinder
2007-03-18 1:29 ` Linus Torvalds
2007-03-18 1:38 ` Nicolas Pitre
2007-03-18 1:55 ` Linus Torvalds
2007-03-18 2:03 ` Nicolas Pitre
2007-03-18 2:20 ` Linus Torvalds
2007-03-18 3:00 ` Nicolas Pitre
2007-03-18 3:31 ` Linus Torvalds
2007-03-18 5:30 ` Julian Phillips
2007-03-18 17:23 ` Linus Torvalds
2007-03-18 10:53 ` Robin Rosenberg
2007-03-18 17:34 ` Linus Torvalds
2007-03-18 18:29 ` Robin Rosenberg
2007-03-18 21:25 ` Shawn O. Pearce
2007-03-19 13:16 ` David Brodsky
2007-03-20 6:35 ` Robin Rosenberg
2007-03-20 9:13 ` David Brodsky
2007-03-21 2:37 ` Linus Torvalds
2007-03-21 2:54 ` Nicolas Pitre
2007-03-18 3:06 ` [PATCH 3/2] Avoid unnecessary strlen() calls Linus Torvalds
2007-03-18 9:45 ` Junio C Hamano
2007-03-18 15:54 ` Linus Torvalds
2007-03-18 15:57 ` Linus Torvalds
2007-03-18 21:38 ` Shawn O. Pearce
2007-03-18 21:48 ` Linus Torvalds
2007-03-20 3:05 ` Johannes Schindelin
2007-03-20 3:29 ` Shawn O. Pearce
2007-03-20 3:40 ` Shawn O. Pearce
2007-03-20 4:11 ` Linus Torvalds [this message]
2007-03-20 4:18 ` Shawn O. Pearce
2007-03-20 4:45 ` Linus Torvalds
2007-03-20 5:44 ` Junio C Hamano
2007-03-20 3:16 ` Junio C Hamano
2007-03-20 4:31 ` Linus Torvalds
2007-03-20 4:39 ` Shawn O. Pearce
2007-03-20 4:57 ` Linus Torvalds
2007-03-18 1:44 ` [PATCH 2/2] Implement a simple delta_base cache Linus Torvalds
2007-03-18 6:28 ` Avi Kivity
2007-03-17 22:44 ` Linus Torvalds
2007-03-16 16:35 ` cleaner/better zlib sources? Jeff Garzik
2007-03-16 16:42 ` Matt Mackall
2007-03-16 16:51 ` Linus Torvalds
2007-03-16 17:12 ` Nicolas Pitre
2007-03-16 23:22 ` Shawn O. Pearce
2007-03-16 17:06 ` Nicolas Pitre
2007-03-16 17:51 ` Linus Torvalds
2007-03-16 18:09 ` Nicolas Pitre
2007-03-16 1:33 ` Davide Libenzi
2007-03-16 2:06 ` Davide Libenzi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.64.0703192052380.6730@woody.linux-foundation.org \
--to=torvalds@linux-foundation.org \
--cc=Johannes.Schindelin@gmx.de \
--cc=git@vger.kernel.org \
--cc=junkio@cox.net \
--cc=mwelinder@gmail.com \
--cc=nico@cam.org \
--cc=spearce@spearce.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).