From d0637c505f8a1d8c4088642f1f3e9e3b22da14f6 Mon Sep 17 00:00:00 2001 From: Barry Song Date: Wed, 20 Jul 2022 21:37:37 +1200 Subject: arm64: enable THP_SWAP for arm64 THP_SWAP has been proven to improve the swap throughput significantly on x86_64 according to commit bd4c82c22c367e ("mm, THP, swap: delay splitting THP after swapped out"). As long as arm64 uses 4K page size, it is quite similar with x86_64 by having 2MB PMD THP. THP_SWAP is architecture-independent, thus, enabling it on arm64 will benefit arm64 as well. A corner case is that MTE has an assumption that only base pages can be swapped. We won't enable THP_SWAP for ARM64 hardware with MTE support until MTE is reworked to coexist with THP_SWAP. A micro-benchmark is written to measure thp swapout throughput as below, unsigned long long tv_to_ms(struct timeval tv) { return tv.tv_sec * 1000 + tv.tv_usec / 1000; } main() { struct timeval tv_b, tv_e;; #define SIZE 400*1024*1024 volatile void *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (!p) { perror("fail to get memory"); exit(-1); } madvise(p, SIZE, MADV_HUGEPAGE); memset(p, 0x11, SIZE); /* write to get mem */ gettimeofday(&tv_b, NULL); madvise(p, SIZE, MADV_PAGEOUT); gettimeofday(&tv_e, NULL); printf("swp out bandwidth: %ld bytes/ms\n", SIZE/(tv_to_ms(tv_e) - tv_to_ms(tv_b))); } Testing is done on rk3568 64bit Quad Core Cortex-A55 platform - ROCK 3A. thp swp throughput w/o patch: 2734bytes/ms (mean of 10 tests) thp swp throughput w/ patch: 3331bytes/ms (mean of 10 tests) Cc: "Huang, Ying" Cc: Minchan Kim Cc: Johannes Weiner Cc: Hugh Dickins Cc: Andrea Arcangeli Cc: Steven Price Cc: Yang Shi Reviewed-by: Anshuman Khandual Signed-off-by: Barry Song Link: https://lore.kernel.org/r/20220720093737.133375-1-21cnbao@gmail.com Signed-off-by: Will Deacon --- include/linux/huge_mm.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'include') diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index de29821231c9..4ddaf6ad73ef 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -461,4 +461,16 @@ static inline int split_folio_to_list(struct folio *folio, return split_huge_page_to_list(&folio->page, list); } +/* + * archs that select ARCH_WANTS_THP_SWAP but don't support THP_SWP due to + * limitations in the implementation like arm64 MTE can override this to + * false + */ +#ifndef arch_thp_swp_supported +static inline bool arch_thp_swp_supported(void) +{ + return true; +} +#endif + #endif /* _LINUX_HUGE_MM_H */ -- cgit v1.2.3