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powerpc: Add threads_per_subcore

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On POWER8 we have a new concept of a subcore. This is what happens when
you take a regular core and split it. A subcore is a grouping of two or
four SMT threads, as well as a handfull of SPRs which allows the subcore
to appear as if it were a core from the point of view of a guest.

Unlike threads_per_core which is fixed at boot, threads_per_subcore can
change while the system is running. Most code will not want to use
threads_per_subcore.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Ellerman 2014-05-23 18:15:27 +10:00 committed by Benjamin Herrenschmidt
parent 8d6f7c5aa3
commit 5853aef1ac
2 changed files with 10 additions and 1 deletions
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7
arch/powerpc/include/asm/cputhreads.h
View File

@ -18,10 +18,12 @@
#ifdef CONFIG_SMP
extern int threads_per_core;
extern int threads_per_subcore;
extern int threads_shift;
extern cpumask_t threads_core_mask;
#else
#define threads_per_core 1
#define threads_per_subcore 1
#define threads_shift 0
#define threads_core_mask (CPU_MASK_CPU0)
#endif
@ -74,6 +76,11 @@ static inline int cpu_thread_in_core(int cpu)
return cpu & (threads_per_core - 1);
}
static inline int cpu_thread_in_subcore(int cpu)
{
return cpu & (threads_per_subcore - 1);
}
static inline int cpu_first_thread_sibling(int cpu)
{
return cpu & ~(threads_per_core - 1);

4
arch/powerpc/kernel/setup-common.c
View File

@ -390,9 +390,10 @@ void __init check_for_initrd(void)
#ifdef CONFIG_SMP
int threads_per_core, threads_shift;
int threads_per_core, threads_per_subcore, threads_shift;
cpumask_t threads_core_mask;
EXPORT_SYMBOL_GPL(threads_per_core);
EXPORT_SYMBOL_GPL(threads_per_subcore);
EXPORT_SYMBOL_GPL(threads_shift);
EXPORT_SYMBOL_GPL(threads_core_mask);
@ -401,6 +402,7 @@ static void __init cpu_init_thread_core_maps(int tpc)
int i;
threads_per_core = tpc;
threads_per_subcore = tpc;
cpumask_clear(&threads_core_mask);
/* This implementation only supports power of 2 number of threads