Index: sys/dev/md/md.c
===================================================================
--- sys/dev/md/md.c
+++ sys/dev/md/md.c
@@ -164,6 +164,9 @@
 static int md_malloc_wait;
 SYSCTL_INT(_vm, OID_AUTO, md_malloc_wait, CTLFLAG_RW, &md_malloc_wait, 0,
     "Allow malloc to wait for memory allocations");
+static int md_direct;
+SYSCTL_INT(_vm, OID_AUTO, md_direct, CTLFLAG_RW, &md_direct, 0,
+    "XXX");
 
 #if defined(MD_ROOT) && !defined(MD_ROOT_FSTYPE)
 #define	MD_ROOT_FSTYPE	"ufs"
@@ -471,10 +474,29 @@
 g_md_start(struct bio *bp)
 {
 	struct md_s *sc;
+	int error;
 
 	sc = bp->bio_to->geom->softc;
 	if ((bp->bio_cmd == BIO_READ) || (bp->bio_cmd == BIO_WRITE)) {
 		devstat_start_transaction_bio(sc->devstat, bp);
+		if (md_direct != 0) {
+			error = sc->start(sc, bp);
+
+			/*
+			 * Devstat uses (bio_bcount, bio_resid) for
+			 * determining the length of the completed part
+			 * of the i/o.  g_io_deliver() will translate
+			 * from bio_completed to that, but it also
+			 * destroys the bio so we must do our own
+			 * translation.
+			 */
+			bp->bio_bcount = bp->bio_length;
+			devstat_end_transaction_bio(sc->devstat, bp);
+
+			bp->bio_completed = bp->bio_length - bp->bio_resid;
+			g_io_deliver(bp, error);
+			return;
+		}
 	}
 	mtx_lock(&sc->queue_mtx);
 	bioq_disksort(&sc->bio_queue, bp);