Re: [PATCH 05/10] x86_64: Use generic percpu

Andi Kleen wrote:
On Friday 28 December 2007 23:05:05 Mike Travis wrote:
Andi Kleen wrote:
On Friday 28 December 2007 01:10:51 travis@xxxxxxx wrote:
x86_64 provides an optimized way to determine the local per cpu area
offset through the pda and determines the base by accessing a remote
pda.
And? The rationale for this patch seems to be incomplete.

As far as I can figure out you're replacing an optimized percpu
implementation which a dumber generic one. Which needs
at least some description why.
The specific intent for the next wave of changes coming are to reduce
[...] That should be in the changelog of the patch.

Anyways the difference between the x86 percpu.h and the generic one is
that x86-64 uses a short cut through the PDA to get the current cpu
offset for the current CPU case. The generic one goes through
smp_processor_id()->array reference instead.

I would request that this optimization is not being removed
without suitable replacement in the same patchkit.

-Andi

I'll take a closer look at this, but it may have to wait until Christoph
is back this Wednesday.

Thanks,
Mike
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