Re: [PATCH 2/2] powerpc: implement arch_scale_smt_power for Power7

From: Joel Schopp
Date: Wed Jan 20 2010 - 17:09:47 EST

+ if (cpu_has_feature(CPU_FTRS_POWER7) && weight == 4) {

I think we should avoid using cpu_has_feature like this. It's better to
create a new feature and add it to POWER7 in the cputable, then check
for that here.

The way that it is now, I think any CPU that has superset of the POWER7
features, will be true here. This is not what we want.
Any ideas for what to call this feature? ASYM_SMT4 ?

+ smt_gain /= weight;

This results in a PPC div, when most of the time it's going to be a
power of two divide. You've optimised the divides a few lines above
this, but not this one. Some consistency would be good.

I can turn that into a conditional branch (case statement) with a shift for the common 1,2,4 cases which should cover all procs available today falling back to a divide for any theoretical future processors that do other numbers of threads.
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