git: 9front

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ref: b683ba218397b21dc41395b9d2451aae76104497
parent: c5580524062896a4c2be829ffeaeb246a7f6a2f7
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Mon Dec 8 22:23:53 EST 2014 

ethervirtio: fix queue notifications and interrupt flags, avoid useless notifications

bug: Rnointerrupt was used on Vqueue.used.flags instead of
Vqueue.avail.flags.

introduce vqnotify() function that notifies the device
about available ring advancement.

avoid queue notifications there that can be slow by
checking Unonotify flag in Vqueue.used.flags.

keep track of the number of notifications in the queue.


--- a/sys/src/9/pc/ethervirtio.c
+++ b/sys/src/9/pc/ethervirtio.c
@@ -137,6 +137,7 @@
 	u16int	lastused;
 
 	uint	nintr;
+	uint	nnote;
 };
 
 struct Ctlr {
@@ -169,6 +170,19 @@
 }
 
 static void
+vqnotify(Ctlr *ctlr, int x)
+{
+	Vqueue *q;
+
+	coherence();
+	q = &ctlr->queue[x];
+	if(q->used->flags & Unonotify)
+		return;
+	q->nnote++;
+	outs(ctlr->port+Qnotify, x);
+}
+
+static void
 txproc(void *v)
 {
 	Vheader *header;
@@ -201,7 +215,7 @@
 		q->desc[j].flags = 0;
 	}
 
-	q->used->flags &= ~Rnointerrupt;
+	q->avail->flags &= ~Rnointerrupt;
 
 	while(waserror())
 		;
@@ -236,7 +250,7 @@
 		q->desc[j].len = BLEN(b);
 		coherence();
 		q->avail->idx++;
-		outs(ctlr->port+Qnotify, Vtxq);
+		vqnotify(ctlr, Vtxq);
 	}
 
 	pexit("ether out queue closed", 1);
@@ -275,7 +289,7 @@
 		q->desc[j].flags = Dwrite;
 	}
 
-	q->used->flags &= ~Rnointerrupt;
+	q->avail->flags &= ~Rnointerrupt;
 
 	while(waserror())
 		;
@@ -294,8 +308,8 @@
 			q->desc[j].len = BALLOC(b);
 			coherence();
 			q->avail->idx++;
-			outs(ctlr->port+Qnotify, Vrxq);
 		} while(q->avail->idx != q->used->idx);
+		vqnotify(ctlr, Vrxq);
 
 		/* wait for any packets to complete */
 		if(!vhasroom(q))
@@ -359,13 +373,13 @@
 	q->availent[i] = 0;
 	coherence();
 
-	q->used->flags &= ~Rnointerrupt;
+	q->avail->flags &= ~Rnointerrupt;
 	q->avail->idx++;
-	outs(ctlr->port+Qnotify, Vctlq);
+	vqnotify(ctlr, Vctlq);
 	while(!vhasroom(q))
 		sleep(q, vhasroom, q);
 	q->lastused = q->used->idx;
-	q->used->flags |= Rnointerrupt;
+	q->avail->flags |= Rnointerrupt;
 
 	qunlock(&ctlr->ctllock);
 	poperror();
@@ -440,8 +454,9 @@
 
 	for(i = 0; i < ctlr->nqueue; i++){
 		q = &ctlr->queue[i];
-		l += snprint(p+l, READSTR-l, "vq%d %#p size %d avail->idx %d used->idx %d lastused %hud nintr %ud\n",
-			i, q, q->qsize, q->avail->idx, q->used->idx, q->lastused, q->nintr);
+		l += snprint(p+l, READSTR-l,
+			"vq%d %#p size %d avail->idx %d used->idx %d lastused %hud nintr %ud nnote %ud\n",
+			i, q, q->qsize, q->avail->idx, q->used->idx, q->lastused, q->nintr, q->nnote);
 	}
 
 	n = readstr(offset, a, n, p);
@@ -520,7 +535,8 @@
 	q->qmask = q->qsize - 1;
 
 	q->lastused = q->avail->idx = q->used->idx = 0;
-	q->used->flags |= Rnointerrupt;
+
+	q->avail->flags |= Rnointerrupt;
 
 	return 0;
 }
-- 
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