> From: Seth Jennings [mailto:sjenning@xxxxxxxxxxxxxxxxxx] > Sent: Thursday, September 29, 2011 8:32 AM > To: gregkh@xxxxxxx > Cc: cascardo@xxxxxxxxxxxxxx; Dan Magenheimer; rdunlap@xxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; Seth Jennings > Subject: [PATCH] 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. > > Based on v3.1-rc7 > > Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> Good catch Seth! Acked-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
