From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Nathan Becker <nbecker@physics.ucsb.edu>
Cc: linux-kernel@vger.kernel.org
Subject: Re: strange CPU speedups with SMP on Athlon 64 X2
Date: Wed, 31 Aug 2005 21:59:40 +1000 [thread overview]
Message-ID: <43159BAC.2080205@yahoo.com.au> (raw)
In-Reply-To: <Pine.LNX.4.63.0508301153340.10786@claven.physics.ucsb.edu>
Nathan Becker wrote:
>
> I would be happy to post my exact C source that I use to do the
> benchmark, but I wanted to get some feedback first in case I'm just
> doing something stupid. Also, since I'm not subscribed to this list,
> please cc me directly regarding this topic.
>
Hi Nathan,
Cache issues may explain this. When 2 processes are allocating
memory in parallel they'll be given different interleavings of
pages which could explain the speedup.
Start one process, get it to memset all its memory, then pause
it and do the same thing. Then set them both running at the same
time (ie. after they've each touched their memory in turn), what
do you see?
(By memset()ing the memory, you'll cause the kernel to actually
allocate a physical page. By doing that one after the other, we
hope to eliminate interleaving issues.)
--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com
prev parent reply other threads:[~2005-08-31 11:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-30 19:16 strange CPU speedups with SMP on Athlon 64 X2 Nathan Becker
2005-08-31 4:51 ` Willy Tarreau
2005-08-31 11:59 ` Nick Piggin [this message]
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=43159BAC.2080205@yahoo.com.au \
--to=nickpiggin@yahoo.com.au \
--cc=linux-kernel@vger.kernel.org \
--cc=nbecker@physics.ucsb.edu \
/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