[BLOCK] Don't pin lots of memory in mempools

Currently we scale the mempool sizes depending on memory installed
in the machine, except for the bio pool itself which sits at a fixed
256 entry pre-allocation.

There's really no point in "optimizing" this OOM path, we just need
enough preallocated to make progress. A single unit is enough, lets
scale it down to 2 just to be on the safe side.

This patch saves ~150kb of pinned kernel memory on a 32-bit box.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

6 files changed, 11 insertions, 40 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 4c2471ee054a..d8121234c347 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -867,7 +867,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
                 goto bad4;
         }
 
-        cc->bs = bioset_create(MIN_IOS, MIN_IOS, 4);
+        cc->bs = bioset_create(MIN_IOS, MIN_IOS);
         if (!cc->bs) {
                 ti->error = "Cannot allocate crypt bioset";
                 goto bad_bs;
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 4eb73d395213..8bdc8a87b249 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -60,7 +60,7 @@ static int resize_pool(unsigned int new_ios)
                 if (!_io_pool)
                         return -ENOMEM;
 
-                _bios = bioset_create(16, 16, 4);
+                _bios = bioset_create(16, 16);
                 if (!_bios) {
                         mempool_destroy(_io_pool);
                         _io_pool = NULL;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 3668b170ea68..11a98df298ec 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1012,7 +1012,7 @@ static struct mapped_device *alloc_dev(int minor)
         if (!md->tio_pool)
                 goto bad3;
 
-        md->bs = bioset_create(16, 16, 4);
+        md->bs = bioset_create(16, 16);
         if (!md->bs)
                 goto bad_no_bioset;
 
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9f7482d0b594..05d79af5ab90 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -31,7 +31,7 @@
 
 
 #define SG_MEMPOOL_NR           ARRAY_SIZE(scsi_sg_pools)
-#define SG_MEMPOOL_SIZE         32
+#define SG_MEMPOOL_SIZE         2
 
 struct scsi_host_sg_pool {
         size_t          size;
diff --git a/fs/bio.c b/fs/bio.c
index 7618bcb18368..693940da4090 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -28,7 +28,7 @@
 #include <linux/blktrace_api.h>
 #include <scsi/sg.h>            /* for struct sg_iovec */
 
-#define BIO_POOL_SIZE 256
+#define BIO_POOL_SIZE 2
 
 static struct kmem_cache *bio_slab __read_mostly;
 
@@ -38,7 +38,7 @@ static struct kmem_cache *bio_slab __read_mostly;
  * a small number of entries is fine, not going to be performance critical.
  * basically we just need to survive
  */
-#define BIO_SPLIT_ENTRIES 8     
+#define BIO_SPLIT_ENTRIES 2
 mempool_t *bio_split_pool __read_mostly;
 
 struct biovec_slab {
@@ -1120,7 +1120,7 @@ struct bio_pair *bio_split(struct bio *bi, mempool_t *pool, int first_sectors)
  * create memory pools for biovec's in a bio_set.
  * use the global biovec slabs created for general use.
  */
-static int biovec_create_pools(struct bio_set *bs, int pool_entries, int scale)
+static int biovec_create_pools(struct bio_set *bs, int pool_entries)
 {
         int i;
 
@@ -1128,9 +1128,6 @@ static int biovec_create_pools(struct bio_set *bs, int pool_entries, int scale)
                 struct biovec_slab *bp = bvec_slabs + i;
                 mempool_t **bvp = bs->bvec_pools + i;
 
-                if (pool_entries > 1 && i >= scale)
-                        pool_entries >>= 1;
-
                 *bvp = mempool_create_slab_pool(pool_entries, bp->slab);
                 if (!*bvp)
                         return -ENOMEM;
@@ -1161,7 +1158,7 @@ void bioset_free(struct bio_set *bs)
         kfree(bs);
 }
 
-struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size, int scale)
+struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size)
 {
         struct bio_set *bs = kzalloc(sizeof(*bs), GFP_KERNEL);
 
@@ -1172,7 +1169,7 @@ struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size, int scale)
         if (!bs->bio_pool)
                 goto bad;
 
-        if (!biovec_create_pools(bs, bvec_pool_size, scale))
+        if (!biovec_create_pools(bs, bvec_pool_size))
                 return bs;
 
 bad:
@@ -1196,38 +1193,12 @@ static void __init biovec_init_slabs(void)
 
 static int __init init_bio(void)
 {
-        int megabytes, bvec_pool_entries;
-        int scale = BIOVEC_NR_POOLS;
-
         bio_slab = kmem_cache_create("bio", sizeof(struct bio), 0,
                                 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
 
         biovec_init_slabs();
 
-        megabytes = nr_free_pages() >> (20 - PAGE_SHIFT);
-
-        /*
-         * find out where to start scaling
-         */
-        if (megabytes <= 16)
-                scale = 0;
-        else if (megabytes <= 32)
-                scale = 1;
-        else if (megabytes <= 64)
-                scale = 2;
-        else if (megabytes <= 96)
-                scale = 3;
-        else if (megabytes <= 128)
-                scale = 4;
-
-        /*
-         * Limit number of entries reserved -- mempools are only used when
-         * the system is completely unable to allocate memory, so we only
-         * need enough to make progress.
-         */
-        bvec_pool_entries = 1 + scale;
-
-        fs_bio_set = bioset_create(BIO_POOL_SIZE, bvec_pool_entries, scale);
+        fs_bio_set = bioset_create(BIO_POOL_SIZE, 2);
         if (!fs_bio_set)
                 panic("bio: can't allocate bios\n");
 
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 08daf3272c02..4d85262b4fa4 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -276,7 +276,7 @@ extern struct bio_pair *bio_split(struct bio *bi, mempool_t *pool,
 extern mempool_t *bio_split_pool;
 extern void bio_pair_release(struct bio_pair *dbio);
 
-extern struct bio_set *bioset_create(int, int, int);
+extern struct bio_set *bioset_create(int, int);
 extern void bioset_free(struct bio_set *);
 
 extern struct bio *bio_alloc(gfp_t, int);