From 59e1a2f4bf83744e748636415fde7d1e9f557e05 Mon Sep 17 00:00:00 2001 From: Timofey Titovets Date: Fri, 28 Dec 2018 00:34:05 -0800 Subject: [PATCH] ksm: replace jhash2 with xxhash Replace jhash2 with xxhash. Perf numbers: Intel(R) Xeon(R) CPU E5-2420 v2 @ 2.20GHz ksm: crc32c hash() 12081 MB/s ksm: xxh64 hash() 8770 MB/s ksm: xxh32 hash() 4529 MB/s ksm: jhash2 hash() 1569 MB/s Sioh Lee did some testing: crc32c_intel: 1084.10ns crc32c (no hardware acceleration): 7012.51ns xxhash32: 2227.75ns xxhash64: 1413.16ns jhash2: 5128.30ns As jhash2 always will be slower (for data size like PAGE_SIZE). Don't use it in ksm at all. Use only xxhash for now, because for using crc32c, cryptoapi must be initialized first - that requires some tricky solution to work well in all situations. Link: http://lkml.kernel.org/r/20181023182554.23464-3-nefelim4ag@gmail.com Signed-off-by: Timofey Titovets Signed-off-by: leesioh Reviewed-by: Pavel Tatashin Reviewed-by: Mike Rapoport Reviewed-by: Andrew Morton Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 1 + mm/ksm.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/Kconfig b/mm/Kconfig index d85e39da47ae..25c71eb8a7db 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -291,6 +291,7 @@ config MMU_NOTIFIER config KSM bool "Enable KSM for page merging" depends on MMU + select XXHASH help Enable Kernel Samepage Merging: KSM periodically scans those areas of an application's address space that an app has advised may be diff --git a/mm/ksm.c b/mm/ksm.c index 5b0894b45ee5..1a088306ef81 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -25,7 +25,7 @@ #include #include #include -#include +#include #include #include #include @@ -1009,7 +1009,7 @@ static u32 calc_checksum(struct page *page) { u32 checksum; void *addr = kmap_atomic(page); - checksum = jhash2(addr, PAGE_SIZE / 4, 17); + checksum = xxhash(addr, PAGE_SIZE, 0); kunmap_atomic(addr); return checksum; }