4045 zfs write throttle & i/o scheduler performance work
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>

@@ -21,10 +21,14 @@
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2013 by Delphix. All rights reserved.
+ */
+
 #include <sys/zfs_context.h>
 #include <sys/dnode.h>
 #include <sys/dmu_objset.h>
 #include <sys/dmu_zfetch.h>
 #include <sys/dmu.h>

@@ -285,11 +289,11 @@
         uint64_t        i;
 
         fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks);
 
         for (i = 0; i < fetchsz; i++) {
-                dbuf_prefetch(dn, blkid + i);
+                dbuf_prefetch(dn, blkid + i, ZIO_PRIORITY_ASYNC_READ);
         }
 
         return (fetchsz);
 }