linux/drivers/staging/zcache, branch v3.3

staging: zcache: fix serialization bug in zv stats

2012-02-08T22:14:14Z

In a multithreaded workload, the zv_curr_dist_counts and zv_cumul_dist_counts statistics are being corrupted because the increments and decrements in zv_create and zv_free are not atomic. This patch converts these statistics and their corresponding increments/decrements/reads to atomic operations. Signed-off-by: Seth Jennings Acked-by: Dan Magenheimer Signed-off-by: Greg Kroah-Hartman

zcache: Set SWIZ_BITS to 8 to reduce tmem bucket lock contention.

2012-02-08T22:14:12Z

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 Signed-off-by: Konrad Rzeszutek Wilk Cc: stable Signed-off-by: Greg Kroah-Hartman

zcache: fix deadlock condition

2012-02-08T22:14:12Z

I discovered this deadlock condition awhile ago working on RAMster but it affects zcache as well. The list spinlock must be locked prior to the page spinlock and released after. As a result, the page copy must also be done while the locks are held. Applies to 3.2. Konrad, please push (via GregKH?)... this is definitely a bug fix so need not be pushed during a -rc0 window. Signed-off-by: Dan Magenheimer Acked-by: Konrad Rzeszutek Wilk Cc: stable Signed-off-by: Greg Kroah-Hartman

Staging: zcache: Fix calls to obsolete function

2011-11-27T02:13:55Z

Function "strict_strtol" replaced by "kstrtol" as suggested by the checkpatch script Signed-off-by: Bernhard Heinloth Signed-off-by: Greg Kroah-Hartman

Merge branch 'staging-next' into Linux 3.1

2011-10-25T07:18:11Z

This was done to resolve a conflict in the drivers/staging/comedi/drivers/ni_labpc.c file that resolved a build bugfix in Linus's tree with a "better" bugfix that was in the staging-next tree that resolved the issue in a more complete manner. Signed-off-by: Greg Kroah-Hartman

staging: zcache: remove zcache_direct_reclaim_lock

2011-10-17T22:24:11Z

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 Reviewed-by: Dave Hansen Acked-by: Dan Magenheimer Signed-off-by: Greg Kroah-Hartman

staging: zcache: reduce tmem bucket lock contention

2011-10-12T15:29:03Z

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 Acked-by: Dan Magenheimer Signed-off-by: Greg Kroah-Hartman

staging: zcache: fix crash on cpu remove

2011-10-11T16:02:49Z

In the case that a cpu is taken offline before zcache_do_preload() is ever called on the cpu, the per-cpu zcache_preloads structure will be uninitialized. In the CPU_DEAD case for zcache_cpu_notifier(), kp->obj is not checked before calling kmem_cache_free() on it. If it is NULL, a crash results. This patch ensures that both kp->obj and kp->page are not NULL before calling the respective free functions. In practice, just checking one or the other should be sufficient since they are assigned together in zcache_do_preload(), but I check both for safety. Signed-off-by: Seth Jennings Acked-by: Dave Hansen Signed-off-by: Greg Kroah-Hartman

staging: zcache: fix cleancache crash

2011-09-20T21:17:13Z

After commit c5f5c4db3938 ("staging: zcache: fix crash on high memory swap") cleancache crashes on the first successful get. This was caused by a remaining virt_to_page() call in zcache_pampd_get_data_and_free() that only gets run in the cleancache path. The patch converts the virt_to_page() to struct page casting like was done for other instances in c5f5c4db3938. Signed-off-by: Seth Jennings Tested-By: Valdis Kletnieks Acked-by: Dan Magenheimer Signed-off-by: Greg Kroah-Hartman Signed-off-by: Linus Torvalds

Merge 3.1-rc4 into staging-next

2011-08-29T15:47:46Z

This resolves a conflict with: drivers/staging/brcm80211/brcmsmac/types.h Signed-off-by: Greg Kroah-Hartman