[PATCHv2 0/2] Add max CPU nodes field to ibm,client-architecture call
Joel Schopp
jschopp at austin.ibm.com
Tue Feb 2 09:50:39 EST 2010
Large NUMA machines require Linux to indicate support for more than 64
cpu cores. This is done through the ibm,client-architecture call, and
is documented in the PAPR. There is also another new field added to
indicate that the OS is Linux as a hint for possible future performance
settings.
The first patch attempts to statically initialize the number of
supported cores with NR_CPUS, the maximum Linux could boot if the cpus
did not have multi-threading (SMT). It can overestimate by the factor
of SMT. For instance on Power6 with 2 way SMT it would overestimate by
a factor of 2. The result of this overestimation is that Linux might
not be able boot all the cpus assigned to it, but would still boot
NR_CPUS worth of SMT threads.
The second patch adjusts for SMT by reading the device tree before
unflattening.
I've updated patch 1 from previous comments. Patch 1 can be taken on its
own if Patch 2 seems like overkill.
v2 - Updated patch 2 style and messages. Basic functionality is the
same as v1.
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