chpstat: Use SI units for default scaling

chpstat uses power-of-two based IEC units such as KiB/s (1024 B/s) when
scaling throughput values in human readable reports. A user interpreting
these numbers can easily be confused by chpstat's default column header
("B/s") to assume that numbers are scaled using power-of-ten based SI
units such as kB/s (1000 B/s).

In addition, users that have worked with similar z/OS tooling to display
channel path activity are used to SI-based scaling, which increases the
chance of chpstat reports being misinterpreted.

To reduce this confusion, use SI units for throughput scaling:

Option          Old factor      New factor
==========================================
--scale k       1024            1000
--scale m       1048576         1000000
--scale g       1073741824      1000000000
--scale auto    IEC units       SI units

Note that machine-readable format produced via option --format is not
affected by scaling.

Reviewed-by: Jimmy Brison <jbrisson@linux.ibm.com>
Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

zconf/chp/chpstat/chpstat.8

@@ -290,7 +290,8 @@ values are:
 
 .IP \(bu 3
 .B auto:
-Scale automatically to fit value into each column. This is the default.
+Scale automatically to fit value into each column. To indicate the current scaling factor,
+an SI-suffix is added to each scaled number (e.g. K for 1000). This is the default.
 .PP
 .IP \(bu 3
 .IR number :
@@ -299,19 +300,19 @@ Scale by
 .PP
 .IP \(bu 3
 .B K:
-Scale by 1024 (KiB)
+Scale by 1000 (KB)
 .PP
 .IP \(bu 3
 .B M:
-Scale by 1,048,576 (MiB)
+Scale by 1,000,000 (MB)
 .PP
 .IP \(bu 3
 .B G:
-Scale by 1,073,741,824 (GiB)
+Scale by 1,000,000,000 (GB)
 .PP
 .IP \(bu 3
 .B T:
-Scale by 1,099,511,627,776 (TiB)
+Scale by 1,000,000,000,000 (TB)
 .PP
 .RE
 

zconf/chp/chpstat/chpstat.c

@@ -459,6 +459,30 @@ static void parse_cmgs(char *arg)
 	}
 }
 
+static bool suffix_to_unit(char *arg, unsigned long *unit_ptr, char *suffix_ptr)
+{
+	const char *suffixes = "KMGT";
+	unsigned long unit, base;
+	size_t len = strlen(arg);
+	char suffix;
+	int i;
+
+	if (len != 1)
+		return false;
+	suffix = (char)toupper(*arg);
+	base = UNIT_DEC;
+	unit = base;
+	for (i = 0; suffixes[i]; i++) {
+		if (suffix == suffixes[i]) {
+			*unit_ptr = unit;
+			*suffix_ptr = suffix;
+			return true;
+		}
+		unit *= base;
+	}
+	return false;
+}
+
 /*
  * Parse a scale unit value in @arg and return the resulting scaling factor.
  */
@@ -467,22 +491,8 @@ static unsigned long parse_unit(char *arg)
 	unsigned long unit;
 	char *endptr;
 
-	if (strlen(arg) == 1) {
-		opts.unit_suffix = (char)toupper(*arg);
-		switch (opts.unit_suffix) {
-		case 'K':
-			return UNIT_BIN;
-		case 'M':
-			return UNIT_BIN * UNIT_BIN;
-		case 'G':
-			return UNIT_BIN * UNIT_BIN * UNIT_BIN;
-		case 'T':
-			return UNIT_BIN * UNIT_BIN * UNIT_BIN * UNIT_BIN;
-		default:
-			break;
-		}
-	}
-	opts.unit_suffix = 0;
+	if (suffix_to_unit(arg, &unit, &opts.unit_suffix))
+		return unit;
 	if (strcmp(arg, "auto") == 0)
 		return UNIT_AUTO;
 	/* Parse as number. */
@@ -1355,7 +1365,7 @@ static void add_pair_value(struct util_rec *table, struct column_t *col,
 		suffix = scale_auto(pair, UNIT_DEC);
 	} else if (pair->unit == CMG_BPS) {
 		if (opts.unit == UNIT_AUTO)
-			suffix = scale_auto(pair, UNIT_BIN);
+			suffix = scale_auto(pair, UNIT_DEC);
 		else
 			scale_fixed(pair, opts.unit);
 	}

zconf/chp/chpstat/column.c

@@ -486,7 +486,7 @@ void column_update_bps_suffix(bool auto_scale, char suffix_char)
 	if (auto_scale)
 		util_asprintf(&str, "(B/s)");
 	else if (suffix_char)
-		util_asprintf(&str, "(%ciB/s)", suffix_char);
+		util_asprintf(&str, "(%cB/s)", suffix_char);
 	else
 		str = util_strdup("(*)");