diff --git a/usr.bin/vmstat/vmstat.c b/usr.bin/vmstat/vmstat.c
--- a/usr.bin/vmstat/vmstat.c
+++ b/usr.bin/vmstat/vmstat.c
@@ -1257,10 +1257,19 @@
 	size_t intrcntlen;
 	uintptr_t kaddr;
 
-	if (kd != NULL) {
+	if (kd != NULL)
 		kread(X_SINTRCNT, &intrcntlen, sizeof(intrcntlen));
-		if ((*intrcnts = malloc(intrcntlen)) == NULL)
-			err(1, "malloc()");
+	else
+		if (mysysctl("hw.intrcnt", NULL, &intrcntlen) != 0)
+			err(1, "mysysctl()");
+
+	if (intrcnts == NULL)
+		return (intrcntlen / sizeof(unsigned long));
+
+	if ((*intrcnts = malloc(intrcntlen)) == NULL)
+		err(1, "malloc()");
+
+	if (kd != NULL) {
 		if (namelist[X_NINTRCNT].n_type == 0)
 			kread(X_INTRCNT, *intrcnts, intrcntlen);
 		else {
@@ -1268,13 +1277,8 @@
 			kreadptr(kaddr, *intrcnts, intrcntlen);
 		}
 	} else {
-		for (*intrcnts = NULL, intrcntlen = 1024; ; intrcntlen *= 2) {
-			*intrcnts = reallocf(*intrcnts, intrcntlen);
-			if (*intrcnts == NULL)
-				err(1, "reallocf()");
-			if (mysysctl("hw.intrcnt", *intrcnts, &intrcntlen) == 0)
-				break;
-		}
+		if (mysysctl("hw.intrcnt", *intrcnts, &intrcntlen) != 0)
+			err(1, "mysysctl()");
 	}
 
 	return (intrcntlen / sizeof(unsigned long));
@@ -1282,31 +1286,30 @@
 
 static void
 print_intrcnts(unsigned long *intrcnts, unsigned long *old_intrcnts,
-    char *intrnames, unsigned int nintr, size_t istrnamlen, long long period_ms)
+    unsigned short namesz, char *intrnames, unsigned int nintr,
+    size_t istrnamlen, long long period_ms)
 {
-	unsigned long *intrcnt, *old_intrcnt;
-	char *intrname;
 	uint64_t inttotal, old_inttotal, total_count, total_rate;
 	unsigned long count, rate;
 	unsigned int i;
 
 	inttotal = 0;
 	old_inttotal = 0;
-	intrname = intrnames;
 	xo_open_list("interrupt");
-	for (i = 0, intrcnt=intrcnts, old_intrcnt=old_intrcnts; i < nintr; i++) {
-		if (intrname[0] != '\0' && (*intrcnt != 0 || aflag)) {
-			count = *intrcnt - *old_intrcnt;
+	for (i = 0; i < nintr; i++) {
+		if (*intrcnts != 0 || (aflag >= 1 && intrnames[0] != '\0') ||
+		    aflag >= 2) {
+			count = *intrcnts - *old_intrcnts;
 			rate = ((uint64_t)count * 1000 + period_ms / 2) / period_ms;
 			xo_open_instance("interrupt");
 			xo_emit("{d:name/%-*s}{ket:name/%s} "
 			    "{:total/%20lu} {:rate/%10lu}\n",
-			    (int)istrnamlen, intrname, intrname, count, rate);
+			    (int)istrnamlen, intrnames, intrnames, count, rate);
 			xo_close_instance("interrupt");
 		}
-		intrname += strlen(intrname) + 1;
-		inttotal += *intrcnt++;
-		old_inttotal += *old_intrcnt++;
+		intrnames += namesz;
+		inttotal += *intrcnts++;
+		old_inttotal += *old_intrcnts++;
 	}
 	total_count = inttotal - old_inttotal;
 	total_rate = (total_count * 1000 + period_ms / 2) / period_ms;
@@ -1323,6 +1326,7 @@
 	char *intrname, *intrnames;
 	long long period_ms, old_uptime, uptime;
 	size_t clen, inamlen, istrnamlen;
+	unsigned short namesz;
 	uintptr_t kaddr;
 	unsigned int nintr;
 
@@ -1341,22 +1345,24 @@
 			kreadptr(kaddr, intrnames, inamlen);
 		}
 	} else {
-		for (intrnames = NULL, inamlen = 1024; ; inamlen *= 2) {
-			if ((intrnames = reallocf(intrnames, inamlen)) == NULL)
-				xo_err(1, "reallocf()");
-			if (mysysctl("hw.intrnames", intrnames, &inamlen) == 0)
-				break;
-		}
+		if (mysysctl("hw.intrnames", NULL, &inamlen) != 0)
+			xo_err(1, "sysctl()");
+		if ((intrnames = malloc(inamlen)) == NULL)
+			xo_err(1, "malloc()");
+		if (mysysctl("hw.intrnames", intrnames, &inamlen) != 0)
+			xo_err(1, "sysctl()");
 	}
 
+	/* Identify the interrupt name length */
+	namesz = inamlen / read_intrcnts(NULL);
+
 	/* Determine the length of the longest interrupt name */
-	intrname = intrnames;
 	istrnamlen = strlen("interrupt");
-	while(*intrname != '\0') {
+	for(intrname = intrnames; intrname < intrnames + inamlen;
+	    intrname += namesz) {
 		clen = strlen(intrname);
 		if (clen > istrnamlen)
 			istrnamlen = clen;
-		intrname += strlen(intrname) + 1;
 	}
 	xo_emit("{T:/%-*s} {T:/%20s} {T:/%10s}\n",
 	    (int)istrnamlen, "interrupt", "total", "rate");
@@ -1380,7 +1386,7 @@
 				xo_err(1, "calloc()");
 		}
 
-		print_intrcnts(intrcnts, old_intrcnts, intrnames, nintr,
+		print_intrcnts(intrcnts, old_intrcnts, namesz, intrnames, nintr,
 		    istrnamlen, period_ms);
 		xo_flush();