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| author | Seth Jennings | 2011-10-04 15:21:32 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2011-10-12 17:29:03 +0200 |
| commit | 3d65c85f9187d311dbf1bf9e7fc2f5091a770853 (patch) | |
| tree | 37d2971a3f6f49693ae706d74e60c010b6ee45c4 /drivers/staging/zcache | |
| parent | staging: brcm80211: remove brcm80211 driver from the staging tree (diff) | |
| download | kernel-qcow2-linux-3d65c85f9187d311dbf1bf9e7fc2f5091a770853.tar.gz kernel-qcow2-linux-3d65c85f9187d311dbf1bf9e7fc2f5091a770853.tar.xz kernel-qcow2-linux-3d65c85f9187d311dbf1bf9e7fc2f5091a770853.zip | |
staging: zcache: reduce tmem bucket lock contention
tmem uses hash buckets each with their own rbtree and lock to
quickly lookup tmem objects. tmem has TMEM_HASH_BUCKETS (256)
buckets per pool. However, because of the way the tmem_oid is
generated for frontswap pages, only 16 unique tmem_oids are being
generated, resulting in only 16 of the 256 buckets being used.
This cause high lock contention for the per bucket locks.
This patch changes SWIZ_BITS to include more bits of the offset.
The result is that all 256 hash buckets are potentially used resulting in a
95% drop in hash bucket lock contention.
Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/staging/zcache')
| -rw-r--r-- | drivers/staging/zcache/zcache-main.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c index dae2f4ee06a6..22b0a7506496 100644 --- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -1804,8 +1804,10 @@ static int zcache_frontswap_poolid = -1; /* * Swizzling increases objects per swaptype, increasing tmem concurrency * for heavy swaploads. Later, larger nr_cpus -> larger SWIZ_BITS + * Setting SWIZ_BITS to 27 basically reconstructs the swap entry from + * frontswap_get_page() */ -#define SWIZ_BITS 4 +#define SWIZ_BITS 27 #define SWIZ_MASK ((1 << SWIZ_BITS) - 1) #define _oswiz(_type, _ind) ((_type << SWIZ_BITS) | (_ind & SWIZ_MASK)) #define iswiz(_ind) (_ind >> SWIZ_BITS) |