diff options
| author | Dan Magenheimer <dan.magenheimer@oracle.com> | 2012-01-23 16:52:20 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-02-13 11:17:04 -0800 |
| commit | c1efec8273372700693661f094324081d8f3ad3d (patch) | |
| tree | b72467fc9880e2e8e45da2e18c5b61155a9ac62f | |
| parent | 57c313f71800dd93f10f6641650dcb4167fa8739 (diff) | |
zcache: Set SWIZ_BITS to 8 to reduce tmem bucket lock contention.
commit e8b4553457e78bcff90f70a31212a40a8fd4f0db upstream.
SWIZ_BITS > 8 results in a much larger number of "tmem_obj"
allocations, likely one per page-placed-in-frontswap. The
tmem_obj is not huge (roughly 100 bytes), but it is large
enough to add a not-insignificant memory overhead to zcache.
The SWIZ_BITS=8 will get roughly the same lock contention
without the space wastage.
The effect of SWIZ_BITS can be thought of as "2^SWIZ_BITS is
the number of unique oids that be generated" (This concept is
limited to frontswap's use of tmem).
Acked-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/staging/zcache/zcache-main.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c index 56c1f9c80dc1..d3a8e6784b86 100644 --- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -1782,9 +1782,9 @@ 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() + * frontswap_get_page(), but has side-effects. Hence using 8. */ -#define SWIZ_BITS 27 +#define SWIZ_BITS 8 #define SWIZ_MASK ((1 << SWIZ_BITS) - 1) #define _oswiz(_type, _ind) ((_type << SWIZ_BITS) | (_ind & SWIZ_MASK)) #define iswiz(_ind) (_ind >> SWIZ_BITS) |