use nil rather than 0 for pointers (finally get all of 'em), and
improve stat collection to be less painful in the common case,
especially on arm.

Reference: /n/atom/patch/qiostats
Date: Wed Sep 23 05:06:18 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/port/qio.c	Wed Sep 23 05:05:44 2015
+++ /sys/src/nix/port/qio.c	Wed Sep 23 05:05:45 2015
@@ -30,7 +30,7 @@
 [Cqbwritepricnt]	"qbwritepricnt",
 };
 
-static uvlong count[Ncount];
+static uvlong count[MACHMAX][Ncount];
 
 static int debugging;
 
@@ -75,28 +75,31 @@
 
 uint	qiomaxatomic = Maxatomic;
 
-extern uvlong ainc64(uvlong*);	/* sic */
-extern uvlong aadd64(uvlong*, uvlong);	/* sic */
-
 static void
 counter(int i)
 {
-	ainc64(count+i);
+	count[m->machno][i]++;
 }
 
 static void
 bytes(int i, int n)
 {
-	aadd64(count+i, n);
+	count[m->machno][i] += n;
 }
 
 char*
 qiostats(char *p, char *e)
 {
-	int i;
+	int i, j;
+	uvlong n;
 
-	for(i = 0; i < Ncount; i++)
-		p = seprint(p, e, "%s %lld\n", countname[i], count[i]);
+	*p = 0;
+	for(i = 0; i < Ncount; i++){
+		n = 0;
+		for(j = 0; j < nelem(count[0]); j++)
+			n += count[j][i];
+		p = seprint(p, e, "%s %lld\n", countname[i], n);
+	}
 
 	return p;
 }
@@ -104,12 +107,12 @@
 void
 ixsummary(void)
 {
-	int i;
+	char buf[1024];
 
 	debugging ^= 1;
 	iallocsummary();
-	for(i = 0; i < Ncount; i++)
-		print("%s %lld\n", countname[i], count[i]);
+	qiostats(buf, buf+sizeof buf);
+	print("%s", buf);
 }
 
 /*
@@ -120,9 +123,9 @@
 {
 	Block *next;
 
-	for(; b != 0; b = next){
+	for(; b != nil; b = next){
 		next = b->next;
-		b->next = 0;
+		b->next = nil;
 		freeb(b);
 	}
 }
@@ -281,7 +284,7 @@
 			counter(Cpullupblockcnt);
 			bp->wp += i;
 			bp->next = nbp->next;
-			nbp->next = 0;
+			nbp->next = nil;
 			freeb(nbp);
 			n -= i;
 			if(n == 0){
@@ -291,7 +294,7 @@
 		}
 	}
 	freeb(bp);
-	return 0;
+	return nil;
 }
 
 /*
@@ -342,7 +345,7 @@
 		bp = bp->next;
 	}
 
-	bp->wp -= (BLEN(bp) - len);
+	bp->wp -= BLEN(bp) - len;
 
 	if(bp->next) {
 		freeblist(bp->next);
@@ -368,7 +371,7 @@
 			return nil;
 	}else
 		nbp = allocb(count);
-	for(; count > 0 && bp != 0; bp = bp->next){
+	for(; count > 0 && bp != nil; bp = bp->next){
 		l = BLEN(bp);
 		if(l > count)
 			l = count;
@@ -467,7 +470,7 @@
 		return nil;
 	}
 	q->bfirst = b->next;
-	b->next = 0;
+	b->next = nil;
 	q->len -= BALLOC(b);
 	q->dlen -= BLEN(b);
 	QDEBUG checkb(b, "qget");
@@ -505,7 +508,7 @@
 		n = BLEN(b);
 		if(n <= len - sofar){
 			q->bfirst = b->next;
-			b->next = 0;
+			b->next = nil;
 			q->len -= BALLOC(b);
 			q->dlen -= BLEN(b);
 			freeb(b);
@@ -556,7 +559,7 @@
 
 	for(;;) {
 		b = q->bfirst;
-		if(b == 0){
+		if(b == nil){
 			q->state |= Qstarve;
 			iunlock(q);
 			return -1;
@@ -584,7 +587,7 @@
 	/* discard the block if we're done with it */
 	if((q->state & Qmsg) || len == n){
 		q->bfirst = b->next;
-		b->next = 0;
+		b->next = nil;
 		q->len -= BALLOC(b);
 		q->dlen -= BLEN(b);
 
@@ -625,8 +628,8 @@
 		return -1;
 	}
 	if(q->state & Qclosed){
-		len = BALLOC(b);
 		iunlock(q);
+		len = BALLOC(b);
 		freeblist(b);
 		return len;
 	}
@@ -674,9 +677,9 @@
 	ilock(q);
 
 	if(q->state & Qclosed){
+		iunlock(q);
 		len = BALLOC(b);
 		freeblist(b);
-		iunlock(q);
 		return len;
 	}
 
@@ -758,7 +761,7 @@
 
 	/* save in buffer */
 	b = iallocb(len);
-	if(b == 0){
+	if(b == nil){
 		iunlock(q);
 		return 0;
 	}
@@ -770,7 +773,7 @@
 	else
 		q->bfirst = b;
 	q->blast = b;
-	/* b->next = 0; done by iallocb() */
+	/* b->next = nil; done by iallocb() */
 	q->len += BALLOC(b);
 	q->dlen += BLEN(b);
 	QDEBUG checkb(b, "qproduce");
@@ -850,8 +853,8 @@
 	Queue *q;
 
 	q = malloc(sizeof(Queue));
-	if(q == 0)
-		return 0;
+	if(q == nil)
+		return nil;
 
 	q->limit = q->inilim = limit;
 	q->kick = kick;
@@ -872,8 +875,8 @@
 	Queue *q;
 
 	q = malloc(sizeof(Queue));
-	if(q == 0)
-		return 0;
+	if(q == nil)
+		return nil;
 
 	q->limit = 0;
 	q->arg = arg;
@@ -888,7 +891,7 @@
 {
 	Queue *q = a;
 
-	return (q->state & Qclosed) || q->bfirst != 0;
+	return (q->state & Qclosed) || q->bfirst != nil;
 }
 
 /*
@@ -1253,7 +1256,7 @@
 	else
 		q->bfirst = b;
 	q->blast = b;
-	b->next = 0;
+	b->next = nil;
 	q->len += BALLOC(b);
 	q->dlen += n;
 	QDEBUG checkb(b, "qbwrite");
@@ -1446,7 +1449,7 @@
 	q->state &= ~(Qflow|Qstarve);
 	strcpy(q->err, Ehungup);
 	bfirst = q->bfirst;
-	q->bfirst = 0;
+	q->bfirst = nil;
 	q->len = 0;
 	q->dlen = 0;
 	q->noblock = 0;
@@ -1470,7 +1473,7 @@
 	/* mark it */
 	ilock(q);
 	q->state |= Qclosed;
-	if(msg == 0 || *msg == 0)
+	if(msg == nil || *msg == 0)
 		strcpy(q->err, Ehungup);
 	else
 		strncpy(q->err, msg, ERRMAX-1);
@@ -1533,7 +1536,7 @@
 int
 qcanread(Queue *q)
 {
-	return q->bfirst!=0;
+	return q->bfirst != nil;
 }
 
 /*
@@ -1565,7 +1568,7 @@
 	/* mark it */
 	ilock(q);
 	bfirst = q->bfirst;
-	q->bfirst = 0;
+	q->bfirst = nil;
 	q->len = 0;
 	q->dlen = 0;
 	iunlock(q);