From: Timofey Titovets <[email protected]> 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/[email protected] Signed-off-by: Timofey Titovets <[email protected]> Signed-off-by: leesioh <[email protected]> Reviewed-by: Pavel Tatashin <[email protected]> Reviewed-by: Mike Rapoport <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: Andrea Arcangeli <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Kirill Tkhai <[email protected]> --- mm/Kconfig | 1 + mm/ksm.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/Kconfig b/mm/Kconfig index d22a5c8d75e2..f5c611b8a342 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -340,6 +340,7 @@ 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 53316ae8057c..1fb8051b22e4 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -23,7 +23,7 @@ #include <linux/pagemap.h> #include <linux/rmap.h> #include <linux/spinlock.h> -#include <linux/jhash.h> +#include <linux/xxhash.h> #include <linux/delay.h> #include <linux/kthread.h> #include <linux/wait.h> @@ -998,7 +998,7 @@ 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; } _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
