[PATCH 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>
---
 kernel/trace/trace_events_hist.c |   72 +++++++++++++++++++++++++++++++-------
 1 file changed, 58 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 1103b9eb0a74..9efb0b9426dd 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;
 		}
 
@@ -5211,14 +5221,31 @@ static inline unsigned int __get_percentage(u64 val, u64 total)
 		return val / (total / 10000);
 }
 
+#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) * size / 10000;
+	int i;
+
+	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);
@@ -5226,8 +5253,11 @@ 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]);
 		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);
 
@@ -5240,9 +5270,13 @@ 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]);
 			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));
@@ -5263,7 +5297,8 @@ 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,
@@ -5272,27 +5307,36 @@ 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);