alistair23-linux/drivers/staging/zcache
Seth Jennings 00bf256011 staging: zcache: remove zcache_direct_reclaim_lock
zcache_do_preload() currently does a spin_trylock() on the
zcache_direct_reclaim_lock. Holding this lock intends to prevent
shrink_zcache_memory() from evicting zbud pages as a result
of a preload.

However, it also prevents two threads from
executing zcache_do_preload() at the same time.  The first
thread will obtain the lock and the second thread's spin_trylock()
will fail (an aborted preload) causing the page to be either lost
(cleancache) or pushed out to the swap device (frontswap). It
also doesn't ensure that the call to shrink_zcache_memory() is
on the same thread as the call to zcache_do_preload().

Additional, there is no need for this mechanism because all
zcache_do_preload() calls that come down from cleancache already
have PF_MEMALLOC set in the process flags which prevents
direct reclaim in the memory manager. If the zcache_do_preload()
call is done from the frontswap path, we _want_ reclaim to be
done (which it isn't right now).

This patch removes the zcache_direct_reclaim_lock and related
statistics in zcache.

Based on v3.1-rc8

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Reviewed-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-10-17 15:24:11 -07:00
..
Kconfig staging: zcache: misc build/config 2011-02-09 15:08:22 -08:00
Makefile staging: fix zcache building 2011-08-02 16:06:18 -07:00
tmem.c Staging: zcache: signedness bug in tmem_get() 2011-08-23 14:52:20 -07:00
tmem.h staging: zcache: support multiple clients, prep for KVM and RAMster 2011-07-08 14:18:53 -07:00
zcache-main.c staging: zcache: remove zcache_direct_reclaim_lock 2011-10-17 15:24:11 -07:00