[PATCH v2 2/2] tracing: Add .graph suffix option to histogram value

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add the .graph suffix which shows the bar graph of the histogram value.

For example, the below example shows that the bar graph
of the histogram of the runtime for each tasks.

------
  # cd /sys/kernel/debug/tracing/
  # echo hist:keys=pid:vals=runtime.graph:sort=pid > \
   events/sched/sched_stat_runtime/trigger
  # sleep 10
  # cat events/sched/sched_stat_runtime/hist
 # event histogram
 #
 # trigger info: hist:keys=pid:vals=hitcount,runtime.graph:sort=pid:size=2048 [active]
 #

 { pid:         14 } hitcount:          2  runtime:
 { pid:         16 } hitcount:          8  runtime:
 { pid:         26 } hitcount:          1  runtime:
 { pid:         57 } hitcount:          3  runtime:
 { pid:         61 } hitcount:         20  runtime: ###
 { pid:         66 } hitcount:          2  runtime:
 { pid:         70 } hitcount:          3  runtime:
 { pid:         72 } hitcount:          2  runtime:
 { pid:        145 } hitcount:         14  runtime: ####################
 { pid:        152 } hitcount:          5  runtime: #######
 { pid:        153 } hitcount:          2  runtime: ####

 Totals:
     Hits: 62
     Entries: 11
     Dropped: 0
-------

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Changes in v2:
  - Show an error when failing to calculate the percentage.
---
 kernel/trace/trace_events_hist.c |   78 +++++++++++++++++++++++++++++++-------
 1 file changed, 64 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index c774d2ff02a8..3d609f457e8c 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -478,6 +478,7 @@ enum hist_field_flags {
 	HIST_FIELD_FL_BUCKET		= 1 << 17,
 	HIST_FIELD_FL_CONST		= 1 << 18,
 	HIST_FIELD_FL_PERCENT		= 1 << 19,
+	HIST_FIELD_FL_GRAPH		= 1 << 20,
 };
 
 struct var_defs {
@@ -1685,6 +1686,8 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
 		flags_str = "usecs";
 	else if (hist_field->flags & HIST_FIELD_FL_PERCENT)
 		flags_str = "percent";
+	else if (hist_field->flags & HIST_FIELD_FL_GRAPH)
+		flags_str = "graph";
 
 	return flags_str;
 }
@@ -2297,6 +2300,10 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
 			if (*flags & (HIST_FIELD_FL_VAR | HIST_FIELD_FL_KEY))
 				goto error;
 			*flags |= HIST_FIELD_FL_PERCENT;
+		} else if (strncmp(modifier, "graph", 5) == 0) {
+			if (*flags & (HIST_FIELD_FL_VAR | HIST_FIELD_FL_KEY))
+				goto error;
+			*flags |= HIST_FIELD_FL_GRAPH;
 		} else {
  error:
 			hist_err(tr, HIST_ERR_BAD_FIELD_MODIFIER, errpos(modifier));
@@ -4266,6 +4273,9 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
 			if (strncmp(field_str + 8, ".percent", 8) == 0)
 				hist_data->fields[HITCOUNT_IDX]->flags |=
 					HIST_FIELD_FL_PERCENT;
+			if (strncmp(field_str + 8, ".graph", 8) == 0)
+				hist_data->fields[HITCOUNT_IDX]->flags |=
+					HIST_FIELD_FL_GRAPH;
 			continue;
 		}
 
@@ -5218,14 +5228,37 @@ static inline unsigned int __get_percentage(u64 val, u64 total)
 	return (unsigned int)div64_ul(val, total);
 }
 
+#define BAR_CHAR '#'
+
+static inline const char *__fill_bar_str(char *buf, int size, u64 val, u64 max)
+{
+	unsigned int len = __get_percentage(val, max);
+	int i;
+
+	if (len == UINT_MAX) {
+		snprintf(buf, size, "[ERROR]");
+		return buf;
+	}
+
+	len = len * size / 10000;
+	for (i = 0; i < len && i < size; i++)
+		buf[i] = BAR_CHAR;
+	while (i < size)
+		buf[i++] = ' ';
+	buf[size] = '\0';
+
+	return buf;
+}
+
 static void hist_trigger_entry_print(struct seq_file *m,
 				     struct hist_trigger_data *hist_data,
-				     u64 *totals,
+				     u64 *maxs,
 				     void *key,
 				     struct tracing_map_elt *elt)
 {
 	const char *field_name;
 	unsigned int i, pc;
+	char bar[21];
 	u64 val;
 
 	hist_trigger_print_key(m, hist_data, key, elt);
@@ -5233,11 +5266,14 @@ static void hist_trigger_entry_print(struct seq_file *m,
 	i = HITCOUNT_IDX;
 	val = tracing_map_read_sum(elt, i);
 	if (hist_data->fields[i]->flags & HIST_FIELD_FL_PERCENT) {
-		pc = __get_percentage(val, totals[i]);
+		pc = __get_percentage(val, maxs[i]);
 		if (pc == UINT_MAX)
 			seq_puts(m, " hitcount:    [ERROR]");
 		else
 			seq_printf(m, " hitcount: %7u.%02u", pc / 100, pc % 100);
+	} else if (hist_data->fields[i]->flags & HIST_FIELD_FL_GRAPH) {
+		seq_printf(m, " hitcount: %20s",
+			   __fill_bar_str(bar, 20, val, maxs[i]));
 	} else
 		seq_printf(m, " hitcount: %10llu", val);
 
@@ -5250,12 +5286,16 @@ static void hist_trigger_entry_print(struct seq_file *m,
 
 		if (hist_data->fields[i]->flags & HIST_FIELD_FL_PERCENT) {
 			val = tracing_map_read_sum(elt, i);
-			pc = __get_percentage(val, totals[i]);
+			pc = __get_percentage(val, maxs[i]);
 			if (pc == UINT_MAX)
 				seq_printf(m, "  %s:    [ERROR]", field_name);
 			else
 				seq_printf(m, "  %s: %7u.%02u", field_name,
 				   pc / 100, pc % 100);
+		} else if (hist_data->fields[i]->flags & HIST_FIELD_FL_GRAPH) {
+			val = tracing_map_read_sum(elt, i);
+			seq_printf(m, "  %s: %20s", field_name,
+				   __fill_bar_str(bar, 20, val, maxs[i]));
 		} else if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
 			seq_printf(m, "  %s: %10llx", field_name,
 				   tracing_map_read_sum(elt, i));
@@ -5276,7 +5316,8 @@ static int print_entries(struct seq_file *m,
 	struct tracing_map_sort_entry **sort_entries = NULL;
 	struct tracing_map *map = hist_data->map;
 	int i, j, n_entries;
-	u64 *totals = NULL;
+	u64 *maxs = NULL;
+	u64 val;
 
 	n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
 					     hist_data->n_sort_keys,
@@ -5285,27 +5326,36 @@ static int print_entries(struct seq_file *m,
 		return n_entries;
 
 	for (j = 0; j < hist_data->n_vals; j++) {
-		if (!(hist_data->fields[j]->flags & HIST_FIELD_FL_PERCENT))
+		if (!(hist_data->fields[j]->flags &
+			(HIST_FIELD_FL_PERCENT | HIST_FIELD_FL_GRAPH)))
 			continue;
-		if (!totals) {
-			totals = kcalloc(hist_data->n_vals, sizeof(u64),
-					 GFP_KERNEL);
-			if (!totals) {
+		if (!maxs) {
+			maxs = kcalloc(hist_data->n_vals, sizeof(u64),
+				       GFP_KERNEL);
+			if (!maxs) {
 				n_entries = -ENOMEM;
 				goto out;
 			}
 		}
-		for (i = 0; i < n_entries; i++)
-			totals[j] += tracing_map_read_sum(
-					sort_entries[i]->elt, j);
+		/*
+		 * If the n-th field shows percentage, the maxs[n] has the
+		 * total, or it has the maximum number.
+		 */
+		for (i = 0; i < n_entries; i++) {
+			val = tracing_map_read_sum(sort_entries[i]->elt, j);
+			if (hist_data->fields[j]->flags & HIST_FIELD_FL_PERCENT)
+				maxs[j] += val;
+			else if (maxs[j] < val)
+				maxs[j] = val;
+		}
 	}
 
 	for (i = 0; i < n_entries; i++)
-		hist_trigger_entry_print(m, hist_data, totals,
+		hist_trigger_entry_print(m, hist_data, maxs,
 					 sort_entries[i]->key,
 					 sort_entries[i]->elt);
 
-	kfree(totals);
+	kfree(maxs);
 out:
 	tracing_map_destroy_sort_entries(sort_entries, n_entries);