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Subject[PATCH v5 4/4] powerpc/64s: enable MMU_LAZY_TLB_SHOOTDOWN
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On a 16-socket 192-core POWER8 system, a context switching benchmark
with as many software threads as CPUs (so each switch will go in and
out of idle), upstream can achieve a rate of about 1 million context
switches per second, due to contention on the mm refcount.

powerpc/64s meets the prerequisites for CONFIG_MMU_LAZY_TLB_SHOOTDOWN,
so enable the option. This increases the above benchmark to 118 million.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/Kconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ba5b66189358..8a584414ef67 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -249,6 +249,7 @@ config PPC
select IRQ_FORCED_THREADING
select MMU_GATHER_PAGE_SIZE
select MMU_GATHER_RCU_TABLE_FREE
+ select MMU_LAZY_TLB_SHOOTDOWN if PPC_BOOK3S_64
select MODULES_USE_ELF_RELA
select NEED_DMA_MAP_STATE if PPC64 || NOT_COHERENT_CACHE
select NEED_SG_DMA_LENGTH
--
2.23.0
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