+ int flags = zio_bulk_flags;
+
+ /*
+ * The smallest buffers (512b) are heavily used and
+ * experience a lot of churn. The slabs allocated
+ * for them are also relatively small (32K). Thus
+ * in over to avoid expensive calls to vmalloc() we
+ * make an exception to the usual slab allocation
+ * policy and force these buffers to be kmem backed.
+ */
+ if (size == (1 << SPA_MINBLOCKSHIFT))
+ flags |= KMC_KMEM;
+