From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> --- 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 642840c..9c011b7 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) -- 1.7.7.5 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
