From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Andi Kleen <ak@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jesse Barnes <jesse.barnes@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: Intel Memory Ordering White Paper
Date: Sat, 8 Sep 2007 06:32:05 +1000 [thread overview]
Message-ID: <200709080632.05389.nickpiggin@yahoo.com.au> (raw)
In-Reply-To: <200709081219.43662.ak@suse.de>
On Saturday 08 September 2007 20:19, Andi Kleen wrote:
> On Friday 07 September 2007 21:57:35 Nick Piggin wrote:
> > > > Anyway, the lfence should be able to go away without so much trouble.
> > >
> > > You mean sfence? lfence in rmb is definitely needed.
> >
> > I mean lfence in smp_rmb().
>
> One point of rmb is to stop speculative loads and I don't think we
> can get that without lfence.
smp_rmb() should not need to do anything because loads are done
in order anyway. Both AMD and Intel have committed to this now.
The important point is that they *appear* to be done in order. AFAIK,
the CPUs can still do speculative and out of order loads, but throw
out the results if they could be wrong.
next prev parent reply other threads:[~2007-09-08 10:34 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-07 22:26 Jesse Barnes
2007-09-08 8:54 ` Nick Piggin
2007-09-07 23:20 ` Linus Torvalds
2007-09-08 17:34 ` Nick Piggin
2007-09-08 17:48 ` Nick Piggin
2007-09-07 18:13 ` Nick Piggin
2007-09-08 8:53 ` Andi Kleen
2007-09-07 19:57 ` Nick Piggin
2007-09-08 10:19 ` Andi Kleen
2007-09-07 20:32 ` Nick Piggin [this message]
2007-09-08 20:37 ` H. Peter Anvin
2007-09-08 11:34 ` dean gaudet
2007-09-08 12:08 ` Petr Vandrovec
2007-09-08 12:27 ` dean gaudet
2007-09-08 10:30 ` Alan Cox
2007-09-07 20:46 ` Nick Piggin
2007-09-08 10:29 ` Alan Cox
2007-09-07 20:49 ` Nick Piggin
2007-09-08 14:11 ` Alan Cox
2007-09-12 18:26 ` Dr. David Alan Gilbert
2007-09-19 16:26 ` Jesse Barnes
2007-09-19 17:29 ` Andi Kleen
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