The patch titled
Subject: ksm: replace jhash2 with xxhash
has been added to the -mm tree. Its filename is
ksm-replace-jhash2-with-xxhash.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ksm-replace-jhash2-with-xxhash.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ksm-replace-jhash2-with-xxhash.patch
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------------------------------------------------------
From: Timofey Titovets <nefelim4ag@xxxxxxxxx>
Subject: 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@xxxxxxxxx
Signed-off-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
Signed-off-by: leesioh <solee@xxxxxxxxxxxxxx>
Reviewed-by: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/Kconfig | 1 +
mm/ksm.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)
--- a/mm/Kconfig~ksm-replace-jhash2-with-xxhash
+++ a/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
--- a/mm/ksm.c~ksm-replace-jhash2-with-xxhash
+++ a/mm/ksm.c
@@ -25,7 +25,7 @@
#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>
@@ -1023,7 +1023,7 @@ static u32 calc_checksum(struct page *pa
{
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;
}
_
Patches currently in -mm which might be from nefelim4ag@xxxxxxxxx are
xxhash-create-arch-dependent-32-64-bit-xxhash.patch
ksm-replace-jhash2-with-xxhash.patch
