Oliver Xymoron wrote:
> On Thu, 27 Jul 2000, Linda Walsh wrote:
>
<snip>
>
> > Talking with an internal engineer here -- NUMA uses MESI
> > cache control similarly to the i386 cache coherency model,
> > so a write of one CPU to a an area of memory will be seen
> > on other processors as soon as they ask for that memory.
>
> That's specific to MIPS. A general Linux NUMA model probably won't assume
> coherence.
>
Why are we not going to assume coherence? What NUMA platforms do we intend
to support in the relevant future that are not CC-NUMA? AFAIK, the only NUMA
platforms we support so far are the SGI Origin 2X00 series (CC-NUMA) and the
Compaq AlphaServer GS* series (also CC-NUMA).
I just don't want generic code to have to pay too heavy a price for future
support of a platform we never support. And truth be told, at that point
we'd be better off just running with Larry's idea of multiple
semi-independent operating systems and handling the lack of cache coherence
in a sane and well-defined way.
- Pete
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