With my previous patch to save bio vector, the size of dm_raid1_read_record
is significantly increased (the vector list takes 3072 bytes on 32-bit machines
and 4096 bytes on 64-bit machines).
The structure dm_raid1_read_record used to be allocated with kmalloc,
but kmalloc aligns the size on the next power-of-two --- so an object
slightly greater than 4096 will allocate 8192 bytes of memory and half of
that memory will be wasted.
This patch turns kmalloc into a slab cache. Slab cache doesn't have this
padding, so it will reduce memory consumption per-request.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/md/dm-raid1.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
Index: linux-2.6.29-rc3-devel/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.29-rc3-devel.orig/drivers/md/dm-raid1.c 2009-02-05 03:26:25.000000000 +0100
+++ linux-2.6.29-rc3-devel/drivers/md/dm-raid1.c 2009-02-05 03:33:54.000000000 +0100
@@ -145,6 +145,8 @@ struct dm_raid1_read_record {
struct dm_bio_details details;
};
+static struct kmem_cache *_dm_raid1_read_record_cache;
+
/*
* Every mirror should look like this one.
*/
@@ -764,9 +766,8 @@ static struct mirror_set *alloc_context(
atomic_set(&ms->suspend, 0);
atomic_set(&ms->default_mirror, DEFAULT_MIRROR);
- len = sizeof(struct dm_raid1_read_record);
- ms->read_record_pool = mempool_create_kmalloc_pool(MIN_READ_RECORDS,
- len);
+ ms->read_record_pool = mempool_create_slab_pool(MIN_READ_RECORDS, _dm_raid1_read_record_cache);
+
if (!ms->read_record_pool) {
ti->error = "Error creating mirror read_record_pool";
kfree(ms);
@@ -1279,16 +1280,31 @@ static int __init dm_mirror_init(void)
{
int r;
+ _dm_raid1_read_record_cache = KMEM_CACHE(dm_raid1_read_record, 0);
+ if (!_dm_raid1_read_record_cache) {
+ DMERR("Can't allocate dm_raid1_read_record cache");
+ r = -ENOMEM;
+ goto bad_cache;
+ }
+
r = dm_register_target(&mirror_target);
- if (r < 0)
+ if (r < 0) {
DMERR("Failed to register mirror target");
+ goto bad_target;
+ }
+
+ return 0;
+bad_target:
+ kmem_cache_destroy(_dm_raid1_read_record_cache);
+bad_cache:
return r;
}
static void __exit dm_mirror_exit(void)
{
dm_unregister_target(&mirror_target);
+ kmem_cache_destroy(_dm_raid1_read_record_cache);
}
/* Module hooks */
--
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