diff options
| author | Anton Blanchard <anton@samba.org> | 2016-10-03 17:40:29 +1100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2016-10-04 16:12:16 +1100 |
| commit | bb85fb5803270c52863b983596c2a038facaf4b3 (patch) | |
| tree | 2995f9570fe4d5a9dbbc50a4f53827ea8252ce8b /arch/powerpc | |
| parent | 91ac730b8b1d7c5e71e7ed2d785a61c27433e13d (diff) | |
powerpc: During context switch, check before setting mm_cpumask
During context switch, switch_mm() sets our current CPU in mm_cpumask.
We can avoid this atomic sequence in most cases by checking before
setting the bit.
Testing on a POWER8 using our context switch microbenchmark:
tools/testing/selftests/powerpc/benchmarks/context_switch \
--process --no-fp --no-altivec --no-vector
Performance improves 2%.
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/include/asm/mmu_context.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h index 475d1be39191..5c451140660a 100644 --- a/arch/powerpc/include/asm/mmu_context.h +++ b/arch/powerpc/include/asm/mmu_context.h @@ -72,7 +72,8 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk) { /* Mark this context has been used on the new CPU */ - cpumask_set_cpu(smp_processor_id(), mm_cpumask(next)); + if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(next))) + cpumask_set_cpu(smp_processor_id(), mm_cpumask(next)); /* 32-bit keeps track of the current PGDIR in the thread struct */ #ifdef CONFIG_PPC32 |