Messages in this thread | | | Date | Wed, 8 May 2002 17:49:25 +0200 | From | Andi Kleen <> | Subject | Re: Memory Barrier Definitions |
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On Wed, May 08, 2002 at 10:27:10AM -0500, Dave Engebretsen wrote: > I am curious what the definition of memory barriers is for IA64, Sparc, > and x86-64. > > >From what I can tell, sparc and x86-64 are like alpha and map directly > to the existing mb, wmb, and rmb semantics, incluing ordering between > system memory and I/O space. Is that an accurate assesment?
I don't think it is true for alpha, but it is true for x86-64. x86-64 by default has strong ordering for most loads/stores. It is possible to use weak ordering for special marked stores. For that there are special read and write and read/write barriers which apply to all memory (not distinction between io space and other memory). In addition there is a way to mark special memory areas as write combining and some other settings, but that is ordered by the normal barriers too.
-Andi
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