Opteron 32-bit or 64-bit

[Arjan van de Ven]

On Tue, 2005-01-25 at 11:48 -0800, Miller, Marc wrote:
> Most existing 32-bit applications should run on the 64-bit version of
> the OS.  Even if you don’t have 64-bit applications, 64-bit RHEL 3 has
> better NUMA scheduling and optimization than the 32-bit version of the
> same operating system.  So in the general case, you will get better
> performance from the 64-bit OS on Opteron than you do from a 32-bit
> OS.

correction; rhel3 does not have NUMA scheduling.

Also I'm not entirely convinced about your argument wrt the case of only
running 32 bit applications:
If you run the 32 bit OS, you will make use of the CAM TLB flush filter,
which makes context switches and such really cheap (kick ass hw feature
btw, thanks guys). If you run the 64 bit OS, you will not make use of
that feature, making context switches somewhat slower.

I'm not entirely convinced that numa memory policy (which is sometimes a
gain, but in a lot of other cases actually a loss) outweighs the loss of
the TLB flush filter.

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