Convert zio_buf_alloc() consumers

In multiple cases zio_buf_alloc() was used instead of kmem_alloc()
or vmem_alloc().  This was often done because the allocations
could be large and it was easy to use zfs_buf_alloc() for them.

But this isn't ideal for allocations which are small or short
lived.  In these cases it is better to use kmem_alloc() or
vmem_alloc().  If possible we want to avoid the case where
we have slabs allocated for kmem caches which are rarely used.

Note for small allocations vmem_alloc() will be internally
converted to kmem_alloc().  Therefore as long as large
allocations are infrequent and short lived the penalty for
using vmem_alloc() is small.

Reviewed-by: Chunwei Chen <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #5409 

1 files changed, 4 insertions, 5 deletions

diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index 6e7a5a0fb..f7857134c 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -1020,7 +1020,7 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
 		int max_bonuslen = DN_SLOTS_TO_BONUSLEN(dn->dn_num_slots);
 
 		ASSERT3U(bonuslen, <=, db->db.db_size);
-		db->db.db_data = zio_buf_alloc(max_bonuslen);
+		db->db.db_data = kmem_alloc(max_bonuslen, KM_SLEEP);
 		arc_space_consume(max_bonuslen, ARC_SPACE_BONUS);
 		if (bonuslen < max_bonuslen)
 			bzero(db->db.db_data, max_bonuslen);
@@ -1132,10 +1132,9 @@ dbuf_fix_old_data(dmu_buf_impl_t *db, uint64_t txg)
 	 */
 	ASSERT(dr->dr_txg >= txg - 2);
 	if (db->db_blkid == DMU_BONUS_BLKID) {
-		/* Note that the data bufs here are zio_bufs */
 		dnode_t *dn = DB_DNODE(db);
 		int bonuslen = DN_SLOTS_TO_BONUSLEN(dn->dn_num_slots);
-		dr->dt.dl.dr_data = zio_buf_alloc(bonuslen);
+		dr->dt.dl.dr_data = kmem_alloc(bonuslen, KM_SLEEP);
 		arc_space_consume(bonuslen, ARC_SPACE_BONUS);
 		bcopy(db->db.db_data, dr->dt.dl.dr_data, bonuslen);
 	} else if (refcount_count(&db->db_holds) > db->db_dirtycnt) {
@@ -2157,7 +2156,7 @@ dbuf_destroy(dmu_buf_impl_t *db)
 		int slots = DB_DNODE(db)->dn_num_slots;
 		int bonuslen = DN_SLOTS_TO_BONUSLEN(slots);
 		ASSERT(db->db.db_data != NULL);
-		zio_buf_free(db->db.db_data, bonuslen);
+		kmem_free(db->db.db_data, bonuslen);
 		arc_space_return(bonuslen, ARC_SPACE_BONUS);
 		db->db_state = DB_UNCACHED;
 	}
@@ -3304,7 +3303,7 @@ dbuf_sync_leaf(dbuf_dirty_record_t *dr, dmu_tx_t *tx)
 		if (*datap != db->db.db_data) {
 			int slots = DB_DNODE(db)->dn_num_slots;
 			int bonuslen = DN_SLOTS_TO_BONUSLEN(slots);
-			zio_buf_free(*datap, bonuslen);
+			kmem_free(*datap, bonuslen);
 			arc_space_return(bonuslen, ARC_SPACE_BONUS);
 		}
 		db->db_data_pending = NULL;