On Thu, 23 Feb 2006, Andrew Morton wrote:
> I'm very much hoping that it is not needed. Would prefer to just toss the
> whole thing away.
>
> What's it supposed to do anyway? Keep wholly-unused pages hanging about in
> each slab cache? If so, it may well be a net loss - it'd be better to push
> those pages back into the page allocator so they can get reused for
> something else while they're possibly still in-cache. Similarly, it's
> better to fall back to the page allocator for a new slab page because
> that's more likely to give us a cache-hot one.
We need _something_ to avoid excessive scanning of cache_cache. It takes a
hell of a lot insmod/rmmod to actually free a full page. Maybe something
like this (totally untested) patch?
Pekka
Index: 2.6-git/drivers/scsi/iscsi_tcp.c
===================================================================
--- 2.6-git.orig/drivers/scsi/iscsi_tcp.c
+++ 2.6-git/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;
Index: 2.6-git/fs/ocfs2/super.c
===================================================================
--- 2.6-git.orig/fs/ocfs2/super.c
+++ 2.6-git/fs/ocfs2/super.c
@@ -959,7 +959,7 @@ static int ocfs2_initialize_mem_caches(v
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;
Index: 2.6-git/include/linux/slab.h
===================================================================
--- 2.6-git.orig/include/linux/slab.h
+++ 2.6-git/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 */
Index: 2.6-git/mm/slab.c
===================================================================
--- 2.6-git.orig/mm/slab.c
+++ 2.6-git/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)
@@ -642,7 +642,6 @@ static struct kmem_cache cache_cache = {
.limit = BOOT_CPUCACHE_ENTRIES,
.shared = 1,
.buffer_size = sizeof(struct kmem_cache),
- .flags = SLAB_NO_REAP,
.spinlock = SPIN_LOCK_UNLOCKED,
.name = "kmem_cache",
#if DEBUG
@@ -1689,9 +1688,6 @@ static inline size_t calculate_slab_orde
* %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.
@@ -3487,8 +3483,7 @@ static void cache_reap(void *unused)
struct slab *slabp;
searchp = list_entry(walk, struct kmem_cache, next);
-
- if (searchp->flags & SLAB_NO_REAP)
+ if (searchp == &cache_cache)
goto next;
check_irq_on();
-
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