[PATCH] riscv: enable THP_SWAP for RV64

Jisheng Zhang
2022-08-21T17:15:21Z

I have a Sipeed Lichee RV dock board which only has 512MB DDR, so
memory optimizations such as swap on zram are helpful. As is seen
in commit d0637c505f8a ("arm64: enable THP_SWAP for arm64") and
commit bd4c82c22c367e ("mm, THP, swap: delay splitting THP after
swapped out"), THP_SWAP can improve the swap throughput significantly.

Enable THP_SWAP for RV64, testing the micro-benchmark which is
introduced by commit d0637c505f8a ("arm64: enable THP_SWAP for arm64")
shows below numbers on the Lichee RV dock board:

thp swp throughput w/o patch: 66908 bytes/ms (mean of 10 tests)
thp swp throughput w/ patch: 322638 bytes/ms (mean of 10 tests)

Improved by 382%!

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
arch/riscv/Kconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index ed66c31e4655..19088c750c7f 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -45,6 +45,7 @@ config RISCV
select ARCH_WANT_FRAME_POINTERS
select ARCH_WANT_GENERAL_HUGETLB
select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
+ select ARCH_WANTS_THP_SWAP if TRANSPARENT_HUGEPAGE
select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
select BUILDTIME_TABLE_SORT if MMU
select CLONE_BACKWARDS
--
2.34.1