[PATCH] slab: Remove SLAB_NO_REAP option

SLAB_NO_REAP is documented as an option that will cause this slab not to be
reaped under memory pressure.  However, that is not what happens.  The only
thing that SLAB_NO_REAP controls at the moment is the reclaim of the unused
slab elements that were allocated in batch in cache_reap().  Cache_reap()
is run every few seconds independently of memory pressure.

Could we remove the whole thing?  Its only used by three slabs anyways and
I cannot find a reason for having this option.

There is an additional problem with SLAB_NO_REAP.  If set then the recovery
of objects from alien caches is switched off.  Objects not freed on the
same node where they were initially allocated will only be reused if a
certain amount of objects accumulates from one alien node (not very likely)
or if the cache is explicitly shrunk.  (Strangely __cache_shrink does not
check for SLAB_NO_REAP)

Getting rid of SLAB_NO_REAP fixes the problems with alien cache freeing.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 4 insertions, 14 deletions

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index ff79e68b347c..7b82ff090d42 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -3639,7 +3639,7 @@ iscsi_tcp_init(void)
 
         taskcache = kmem_cache_create("iscsi_taskcache",
                         sizeof(struct iscsi_data_task), 0,
-                        SLAB_HWCACHE_ALIGN | SLAB_NO_REAP, NULL, NULL);
+                        SLAB_HWCACHE_ALIGN, NULL, NULL);
         if (!taskcache)
                 return -ENOMEM;
 
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 8dd3aafec499..09e1c57a86a0 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -959,7 +959,7 @@ static int ocfs2_initialize_mem_caches(void)
         ocfs2_lock_cache = kmem_cache_create("ocfs2_lock",
                                              sizeof(struct ocfs2_journal_lock),
                                              0,
-                                             SLAB_NO_REAP|SLAB_HWCACHE_ALIGN,
+                                             SLAB_HWCACHE_ALIGN,
                                              NULL, NULL);
         if (!ocfs2_lock_cache)
                 return -ENOMEM;
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 38bed95dda7a..2b28c849d75a 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -38,7 +38,6 @@ typedef struct kmem_cache kmem_cache_t;
 #define SLAB_DEBUG_INITIAL      0x00000200UL    /* Call constructor (as verifier) */
 #define SLAB_RED_ZONE           0x00000400UL    /* Red zone objs in a cache */
 #define SLAB_POISON             0x00000800UL    /* Poison objects */
-#define SLAB_NO_REAP            0x00001000UL    /* never reap from the cache */
 #define SLAB_HWCACHE_ALIGN      0x00002000UL    /* align objs on a h/w cache lines */
 #define SLAB_CACHE_DMA          0x00004000UL    /* use GFP_DMA memory */
 #define SLAB_MUST_HWCACHE_ALIGN 0x00008000UL    /* force alignment */
diff --git a/mm/slab.c b/mm/slab.c
index 5c2574989834..24235506b2a0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -170,12 +170,12 @@
 #if DEBUG
 # define CREATE_MASK    (SLAB_DEBUG_INITIAL | SLAB_RED_ZONE | \
                          SLAB_POISON | SLAB_HWCACHE_ALIGN | \
-                         SLAB_NO_REAP | SLAB_CACHE_DMA | \
+                         SLAB_CACHE_DMA | \
                          SLAB_MUST_HWCACHE_ALIGN | SLAB_STORE_USER | \
                          SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
                          SLAB_DESTROY_BY_RCU)
 #else
-# define CREATE_MASK    (SLAB_HWCACHE_ALIGN | SLAB_NO_REAP | \
+# define CREATE_MASK    (SLAB_HWCACHE_ALIGN | \
                          SLAB_CACHE_DMA | SLAB_MUST_HWCACHE_ALIGN | \
                          SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
                          SLAB_DESTROY_BY_RCU)
@@ -662,7 +662,6 @@ static struct kmem_cache cache_cache = {
         .limit = BOOT_CPUCACHE_ENTRIES,
         .shared = 1,
         .buffer_size = sizeof(struct kmem_cache),
-        .flags = SLAB_NO_REAP,
         .name = "kmem_cache",
 #if DEBUG
         .obj_size = sizeof(struct kmem_cache),
@@ -1848,9 +1847,6 @@ static void setup_cpu_cache(struct kmem_cache *cachep)
  * %SLAB_RED_ZONE - Insert `Red' zones around the allocated memory to check
  * for buffer overruns.
  *
- * %SLAB_NO_REAP - Don't automatically reap this cache when we're under
- * memory pressure.
- *
  * %SLAB_HWCACHE_ALIGN - Align the objects in this cache to a hardware
  * cacheline.  This can be beneficial if you're counting cycles as closely
  * as davem.
@@ -3584,10 +3580,6 @@ static void cache_reap(void *unused)
                 struct slab *slabp;
 
                 searchp = list_entry(walk, struct kmem_cache, next);
-
-                if (searchp->flags & SLAB_NO_REAP)
-                        goto next;
-
                 check_irq_on();
 
                 l3 = searchp->nodelists[numa_node_id()];
@@ -3635,7 +3627,6 @@ static void cache_reap(void *unused)
                 } while (--tofree > 0);
 next_unlock:
                 spin_unlock_irq(&l3->list_lock);
-next:
                 cond_resched();
         }
         check_irq_on();