Index: lib/libutil/humanize_number.3
===================================================================
--- lib/libutil/humanize_number.3	(revision 317681)
+++ lib/libutil/humanize_number.3	(working copy)
@@ -28,7 +28,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd October 7, 2013
+.Dd May 3, 2017
 .Dt HUMANIZE_NUMBER 3
 .Os
 .Sh NAME
@@ -139,6 +139,10 @@
 The following flags may be passed in
 .Fa flags :
 .Bl -tag -width ".Dv HN_DIVISOR_1000" -offset indent
+.It Dv HN_FRACTIONAL
+Display up to two additional fractional digits if they would fit,
+unless the value was so small (i.e. less than 1000 or less than 1024)
+that it wouldn't make sense.
 .It Dv HN_DECIMAL
 If the final result is less than 10, display it using one decimal place.
 .It Dv HN_NOSPACE
Index: lib/libutil/humanize_number.c
===================================================================
--- lib/libutil/humanize_number.c	(revision 317681)
+++ lib/libutil/humanize_number.c	(working copy)
@@ -157,13 +157,43 @@
 		}
 	}
 
-	/* If a value <= 9.9 after rounding and ... */
 	/*
-	 * XXX - should we make sure there is enough space for the decimal
-	 * place and if not, don't do HN_DECIMAL?
+	 * Generate base output
 	 */
-	if (((quotient == 9 && remainder < divisordeccut) || quotient < 9) &&
-	    i > 0 && flags & HN_DECIMAL) {
+	r = snprintf(buf, len, "%" PRId64 "%s%s%s",
+	    sign * (quotient + (remainder + divisor / 2) / divisor),
+	    sep, SCALE2PREFIX(i), suffix);
+
+	if ((flags & HN_FRACTIONAL) && (u_int)r + 3 <= len && i) {
+		/*
+		 * If FRACTIONAL is specified output up to two fractional
+		 * digits, unless the value was not divided out.
+		 */
+		int64_t frac;
+		int n;
+
+		n = (int)len - r - 2;
+		frac = 1;
+		if (n > 2)	/* max 2 fractional digits */
+			n = 2;
+
+		while (n) {
+			frac = frac * 10;
+			--n;
+		}
+		s1 = (int)quotient + ((remainder * frac + divisor / 2) /
+		    divisor / frac);
+		s2 = ((remainder * frac + divisor / 2) / divisor) % frac;
+		r = snprintf(buf, len, "%d%s%d%s%s%s",
+		    sign * s1, localeconv()->decimal_point, s2,
+		    sep, SCALE2PREFIX(i), suffix);
+	} else if ((flags & HN_DECIMAL) && (u_int)r + 3 <= len &&
+		(((quotient == 9 && remainder < divisordeccut) ||
+		    quotient < 9) && i > 0)) {
+		/*
+		 * If DECIMAL is specified and the value is <= 9.9 after
+		 * rounding, and it fits, add one fractional digit.
+		 */
 		s1 = (int)quotient + ((remainder * 10 + divisor / 2) /
 		    divisor / 10);
 		s2 = ((remainder * 10 + divisor / 2) / divisor) % 10;
@@ -170,10 +200,6 @@
 		r = snprintf(buf, len, "%d%s%d%s%s%s",
 		    sign * s1, localeconv()->decimal_point, s2,
 		    sep, SCALE2PREFIX(i), suffix);
-	} else
-		r = snprintf(buf, len, "%" PRId64 "%s%s%s",
-		    sign * (quotient + (remainder + divisor / 2) / divisor),
-		    sep, SCALE2PREFIX(i), suffix);
-
+	}
 	return (r);
 }
Index: lib/libutil/libutil.h
===================================================================
--- lib/libutil/libutil.h	(revision 317681)
+++ lib/libutil/libutil.h	(working copy)
@@ -223,6 +223,7 @@
 #define	HN_B			0x04
 #define	HN_DIVISOR_1000		0x08
 #define	HN_IEC_PREFIXES		0x10
+#define	HN_FRACTIONAL		0x20
 
 /* Values for humanize_number(3)'s scale parameter. */
 #define	HN_GETSCALE		0x10
Index: bin/df/df.c
===================================================================
--- bin/df/df.c	(revision 317681)
+++ bin/df/df.c	(working copy)
@@ -72,6 +72,10 @@
 #define UNITS_SI	1
 #define UNITS_2		2
 
+#ifndef HN_FRACTIONAL
+#define	HN_FRACTIONAL	HN_DECIMAL
+#endif
+
 /* Maximum widths of various fields. */
 struct maxwidths {
 	int	mntfrom;
@@ -410,10 +414,10 @@
 static void
 prthumanval(const char *fmt, int64_t bytes)
 {
-	char buf[6];
+	char buf[7];
 	int flags;
 
-	flags = HN_B | HN_NOSPACE | HN_DECIMAL;
+	flags = HN_B | HN_NOSPACE | HN_FRACTIONAL;
 	if (hflag == UNITS_SI)
 		flags |= HN_DIVISOR_1000;
 
@@ -433,7 +437,7 @@
 	char buf[6];
 	int flags;
 
-	flags = HN_NOSPACE | HN_DECIMAL | HN_DIVISOR_1000;
+	flags = HN_NOSPACE | HN_FRACTIONAL | HN_DIVISOR_1000;
 
 	humanize_number(buf, sizeof(buf) - (bytes < 0 ? 0 : 1),
 	    bytes, "", HN_AUTOSCALE, flags);
Index: usr.sbin/pstat/pstat.c
===================================================================
--- usr.sbin/pstat/pstat.c	(revision 317681)
+++ usr.sbin/pstat/pstat.c	(working copy)
@@ -72,6 +72,10 @@
 #include <string.h>
 #include <unistd.h>
 
+#ifndef HN_FRACTIONAL
+#define	HN_FRACTIONAL	HN_DECIMAL
+#endif
+
 enum {
 	NL_CONSTTY,
 	NL_MAXFILES,
@@ -492,10 +496,10 @@
 	if (humanflag) {
 		humanize_number(usedbuf, sizeof(usedbuf),
 		    CONVERT_BLOCKS(bused), "",
-		    HN_AUTOSCALE, HN_B | HN_NOSPACE | HN_DECIMAL);
+		    HN_AUTOSCALE, HN_B | HN_NOSPACE | HN_FRACTIONAL);
 		humanize_number(availbuf, sizeof(availbuf),
 		    CONVERT_BLOCKS(bavail), "",
-		    HN_AUTOSCALE, HN_B | HN_NOSPACE | HN_DECIMAL);
+		    HN_AUTOSCALE, HN_B | HN_NOSPACE | HN_FRACTIONAL);
 		printf("%8s %8s %5.0f%%\n", usedbuf, availbuf, bpercent);
 	} else {
 		printf("%8jd %8jd %5.0f%%\n", (intmax_t)CONVERT(bused),