From: Linus Torvalds <torvalds@linux-foundation.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Nick Piggin <npiggin@suse.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andi Kleen <ak@suse.de>
Subject: Re: [patch] x86: improved memory barrier implementation
Date: Fri, 28 Sep 2007 09:15:06 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.0.999.0709280911100.3579@woody.linux-foundation.org> (raw)
In-Reply-To: <20070928170719.2f617a7a@the-village.bc.nu>
On Fri, 28 Sep 2007, Alan Cox wrote:
>
> However
> - You've not shown the patch has any performance gain
It would be nice to see this.
> - You've probably broken Pentium Pro
Probably not a big deal, but yeah, we should have that broken-ppro option.
> - and for modern processors its still not remotely clear your patch is
> correct because of NT stores.
This one I disagree with. The *old* code doesn't honor NT stores *either*.
The fact is, if you use NT stores and then depend on ordering, it has
nothing what-so-ever to do with spinlocks or smp_[rw]mb. You need to use
the DMA barriers (ie the non-smp ones).
The non-temporal stores should be basically considered to be "IO", not any
normal memory operation.
Linus
next prev parent reply other threads:[~2007-09-28 16:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-28 15:48 Nick Piggin
2007-09-28 16:07 ` Alan Cox
2007-09-28 16:15 ` Linus Torvalds [this message]
2007-09-29 13:17 ` Nick Piggin
2007-09-29 16:07 ` Linus Torvalds
2007-09-30 12:16 ` Nick Piggin
2007-09-28 16:54 ` Nick Piggin
2007-09-28 17:18 ` Alan Cox
2007-09-29 13:19 ` Nick Piggin
2007-09-30 1:43 ` Dave Jones
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=alpine.LFD.0.999.0709280911100.3579@woody.linux-foundation.org \
--to=torvalds@linux-foundation.org \
--cc=ak@suse.de \
--cc=alan@lxorguk.ukuu.org.uk \
--cc=linux-kernel@vger.kernel.org \
--cc=npiggin@suse.de \
/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
all inboxes | Powered by JetHome®