Re: Intel Memory Ordering White Paper

Nick Piggin
2007-09-08T10:52:34Z

On Saturday 08 September 2007 20:29, Alan Cox wrote:
> On Fri, 7 Sep 2007 15:26:50 -0700
>
> Jesse Barnes <jesse.barnes@intel.com> wrote:
> > FYI, we just released a new white paper describing memory ordering for
> > Intel processors:
> > http://developer.intel.com/products/processor/manuals/index.htm
> >
> > Should help answer some questions about some of the ordering primitives
> > we use on i386 and x86_64.
>
> Nice - but it appears to be 64bit only - and indeed it appears to be
> untrue for real 32bit because of the Pentium Pro fencing errata.

As I said, we're not doing anything special in barriers for the ppro errata
today anyway.

> The kernel also runs on IDT Winchip, Cyrix and AMD processors not all of
> which have exactly the same behaviour (the IDT Winchip as we run it
> profoundly differs)

AMD processors guarantee loads are ordered and stores are ordered
(with exceptions of non-temporal, and non-wb policy).

As for the others that do out of order stores, are any of them SMP?