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authorAnton Blanchard <anton@samba.org>2016-10-03 17:40:29 +1100
committerMichael Ellerman <mpe@ellerman.id.au>2016-10-04 16:12:16 +1100
commitbb85fb5803270c52863b983596c2a038facaf4b3 (patch)
tree2995f9570fe4d5a9dbbc50a4f53827ea8252ce8b /arch/powerpc
parent91ac730b8b1d7c5e71e7ed2d785a61c27433e13d (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.h3
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