From: krw <krw@openbsd.org>
Date: Wed, 31 May 2017 08:10:24 +0000 (+0000)
Subject: Optimize virtio_enqueue_trim() a bit by nuking unneeded
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=cf707a04dc7469fdb7a4037ad0e56f6c5a9295a0;p=openbsd

Optimize virtio_enqueue_trim() a bit by nuking unneeded
re-initializations of statically set fields. Move a common
chunk out of both clauses of if/else.

No intentional functional change.

ok sf@
---

diff --git a/sys/dev/pv/virtio.c b/sys/dev/pv/virtio.c
index 116e1002d09..3107ee8c9ac 100644
--- a/sys/dev/pv/virtio.c
+++ b/sys/dev/pv/virtio.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: virtio.c,v 1.9 2017/05/30 19:28:09 sf Exp $	*/
+/*	$OpenBSD: virtio.c,v 1.10 2017/05/31 08:10:24 krw Exp $	*/
 /*	$NetBSD: virtio.c,v 1.3 2011/11/02 23:05:52 njoly Exp $	*/
 
 /*
@@ -735,37 +735,27 @@ virtio_enqueue_trim(struct virtqueue *vq, int slot, int nsegs)
 {
 	struct vq_entry *qe1 = &vq->vq_entries[slot];
 	struct vring_desc *vd = &vq->vq_desc[0];
-	struct vq_entry *qe;
-	int i, s;
+	int i;
 
 	if ((vd[slot].flags & VRING_DESC_F_INDIRECT) == 0) {
-		qe1->qe_indirect = 0;
-		qe1->qe_desc_base = vd;
 		qe1->qe_next = qe1->qe_index;
-
 		/*
 		 * N.B.: the vq_entries are ASSUMED to be a contiguous
 		 *       block with slot being the index to the first one.
 		 */
-		s = slot;
-		for (i = 0; i < nsegs - 1; i++) {
-			qe = &vq->vq_entries[s+1];
-			vd[s].flags = VRING_DESC_F_NEXT;
-			vd[s].next = qe->qe_index;
-			s = qe->qe_index;
-		}
-		vd[s].flags = 0;
 	} else {
+		qe1->qe_next = 0;
 		vd = &vq->vq_desc[qe1->qe_index];
 		vd->len = sizeof(struct vring_desc) * nsegs;
 		vd = qe1->qe_desc_base;
-		for (i = 0; i < nsegs; i++) {
-			vd[i].flags = VRING_DESC_F_NEXT;
-			if (i == (nsegs - 1))
-				vd[i].flags = 0;
-		}
-		qe1->qe_next = 0;
+		slot = 0;
+	}
+
+	for (i = 0; i < nsegs -1 ; i++) {
+		vd[slot].flags = VRING_DESC_F_NEXT;
+		slot++;
 	}
+	vd[slot].flags = 0;
 }
 
 /*