[PATCH v4 4/5] 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 v3:
  - Show hitcount.graph in trigger info correctly.
  - Show both hitcount.percent and hitcount.graph on the same histogram.
 Changes in v2:
  - Show an error when failing to calculate the percentage.
---
 kernel/trace/trace_events_hist.c |   82 +++++++++++++++++++++++++++++++-------
 1 file changed, 66 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index af6c140f85e6..fceea784fded 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -507,6 +507,7 @@ 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 {
@@ -1710,6 +1711,8 @@ 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;
 }
@@ -2322,6 +2325,10 @@ 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));
@@ -4362,6 +4369,9 @@ 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;
 		}
 
@@ -5316,20 +5326,52 @@ static inline unsigned int __get_percentage(u64 val, u64 total)
 	return val ? UINT_MAX : 0;
 }
 
+#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;
+}
+
+struct hist_val_stat {
+	u64 max;
+	u64 total;
+};
+
 static void hist_trigger_print_val(struct seq_file *m, unsigned int idx,
 				   const char *field_name, unsigned long flags,
-				   u64 *totals, struct tracing_map_elt *elt)
+				   struct hist_val_stat *stats,
+				   struct tracing_map_elt *elt)
 {
 	u64 val = tracing_map_read_sum(elt, idx);
 	unsigned int pc;
+	char bar[21];
 
 	if (flags & HIST_FIELD_FL_PERCENT) {
-		pc = __get_percentage(val, totals[idx]);
+		pc = __get_percentage(val, stats[idx].total);
 		if (pc == UINT_MAX)
 			seq_printf(m, " %s (%%):[ERROR]", field_name);
 		else
 			seq_printf(m, " %s (%%): %3u.%02u", field_name,
 					pc / 100, pc % 100);
+	} else if (flags & HIST_FIELD_FL_GRAPH) {
+		seq_printf(m, " %s: %20s", field_name,
+			   __fill_bar_str(bar, 20, val, stats[idx].max));
 	} else if (flags & HIST_FIELD_FL_HEX) {
 		seq_printf(m, " %s: %10llx", field_name, val);
 	} else {
@@ -5339,7 +5381,7 @@ static void hist_trigger_print_val(struct seq_file *m, unsigned int idx,
 
 static void hist_trigger_entry_print(struct seq_file *m,
 				     struct hist_trigger_data *hist_data,
-				     u64 *totals,
+				     struct hist_val_stat *stats,
 				     void *key,
 				     struct tracing_map_elt *elt)
 {
@@ -5350,7 +5392,7 @@ static void hist_trigger_entry_print(struct seq_file *m,
 	hist_trigger_print_key(m, hist_data, key, elt);
 
 	flags = hist_data->fields[i]->flags;
-	hist_trigger_print_val(m, i, "hitcount", flags, totals, elt);
+	hist_trigger_print_val(m, i, "hitcount", flags, stats, elt);
 
 	for (i = 1; i < hist_data->n_vals; i++) {
 		field_name = hist_field_name(hist_data->fields[i], 0);
@@ -5360,7 +5402,7 @@ static void hist_trigger_entry_print(struct seq_file *m,
 			continue;
 
 		seq_puts(m, " ");
-		hist_trigger_print_val(m, i, field_name, flags, totals, elt);
+		hist_trigger_print_val(m, i, field_name, flags, stats, elt);
 	}
 
 	print_actions(m, hist_data, elt);
@@ -5374,7 +5416,8 @@ 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;
+	struct hist_val_stat *stats = NULL;
+	u64 val;
 
 	n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
 					     hist_data->n_sort_keys,
@@ -5382,28 +5425,33 @@ static int print_entries(struct seq_file *m,
 	if (n_entries < 0)
 		return n_entries;
 
+	/* Calculate the max and the total for each field if needed. */
 	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 (!stats) {
+			stats = kcalloc(hist_data->n_vals, sizeof(*stats),
+				       GFP_KERNEL);
+			if (!stats) {
 				n_entries = -ENOMEM;
 				goto out;
 			}
 		}
-		for (i = 0; i < n_entries; i++)
-			totals[j] += tracing_map_read_sum(
-					sort_entries[i]->elt, j);
+		for (i = 0; i < n_entries; i++) {
+			val = tracing_map_read_sum(sort_entries[i]->elt, j);
+			stats[j].total += val;
+			if (stats[j].max < val)
+				stats[j].max = val;
+		}
 	}
 
 	for (i = 0; i < n_entries; i++)
-		hist_trigger_entry_print(m, hist_data, totals,
+		hist_trigger_entry_print(m, hist_data, stats,
 					 sort_entries[i]->key,
 					 sort_entries[i]->elt);
 
-	kfree(totals);
+	kfree(stats);
 out:
 	tracing_map_destroy_sort_entries(sort_entries, n_entries);
 
@@ -5828,6 +5876,8 @@ static int event_hist_trigger_print(struct seq_file *m,
 			seq_puts(m, "hitcount");
 			if (field->flags & HIST_FIELD_FL_PERCENT)
 				seq_puts(m, ".percent");
+			else if (field->flags & HIST_FIELD_FL_GRAPH)
+				seq_puts(m, ".graph");
 		} else {
 			seq_puts(m, ",");
 			hist_field_print(m, field);