xxhash much faster then jhash,
ex. for x86_64 host:
PAGE_SIZE: 4096, loop count: 1048576
jhash2: 0xacbc7a5b time: 1907 ms, th: 2251.9 MiB/s
xxhash32: 0x570da981 time: 739 ms, th: 5809.4 MiB/s
xxhash64: 0xa1fa032ab85bbb62 time: 371 ms, th: 11556.6 MiB/s
xxhash64 on x86_32 work with ~ same speed as jhash2.
xxhash32 on x86_32 work with ~ same speed as for x86_64
So replace jhash with xxhash,
and use fastest version for current target ARCH.
Signed-off-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
---
mm/Kconfig | 1 +
mm/ksm.c | 25 ++++++++++++++++++-------
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index 9c4bdddd80c2..252ab266ac23 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -305,6 +305,7 @@ 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 15dd7415f7b3..e012d9778c18 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -25,7 +25,8 @@
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/spinlock.h>
-#include <linux/jhash.h>
+#include <linux/xxhash.h>
+#include <linux/bitops.h> /* BITS_PER_LONG */
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/wait.h>
@@ -51,6 +52,12 @@
#define DO_NUMA(x) do { } while (0)
#endif
+#if BITS_PER_LONG == 64
+typedef u64 xxhash;
+#else
+typedef u32 xxhash;
+#endif
+
/*
* A few notes about the KSM scanning process,
* to make it easier to understand the data structures below:
@@ -186,7 +193,7 @@ struct rmap_item {
};
struct mm_struct *mm;
unsigned long address; /* + low bits used for flags below */
- unsigned int oldchecksum; /* when unstable */
+ xxhash oldchecksum; /* when unstable */
union {
struct rb_node node; /* when node of unstable tree */
struct { /* when listed from stable tree */
@@ -255,7 +262,7 @@ static unsigned int ksm_thread_pages_to_scan = 100;
static unsigned int ksm_thread_sleep_millisecs = 20;
/* Checksum of an empty (zeroed) page */
-static unsigned int zero_checksum __read_mostly;
+static xxhash zero_checksum __read_mostly;
/* Whether to merge empty (zeroed) pages with actual zero pages */
static bool ksm_use_zero_pages __read_mostly;
@@ -982,11 +989,15 @@ static int unmerge_and_remove_all_rmap_items(void)
}
#endif /* CONFIG_SYSFS */
-static u32 calc_checksum(struct page *page)
+static xxhash calc_checksum(struct page *page)
{
- u32 checksum;
+ xxhash checksum;
void *addr = kmap_atomic(page);
- checksum = jhash2(addr, PAGE_SIZE / 4, 17);
+#if BITS_PER_LONG == 64
+ checksum = xxh64(addr, PAGE_SIZE, 0);
+#else
+ checksum = xxh32(addr, PAGE_SIZE, 0);
+#endif
kunmap_atomic(addr);
return checksum;
}
@@ -1994,7 +2005,7 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
struct page *tree_page = NULL;
struct stable_node *stable_node;
struct page *kpage;
- unsigned int checksum;
+ xxhash checksum;
int err;
bool max_page_sharing_bypass = false;
--
2.14.1
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
