[PATCH v8 09/23] tracing: Add hist trigger support for multiple values ('vals=' param)

[Tom Zanussi]

Allow users to specify trace event fields to use in aggregated sums
via a new 'vals=' keyword.  Before this addition, the only aggregated
sum supported was the implied value 'hitcount'.  With this addition,
'hitcount' is also supported as an explicit value field, as is any
numeric trace event field.

This expands the hist trigger syntax from this:

  # echo hist:keys=xxx [ if filter] > event/trigger

to this:

  # echo hist:keys=xxx:vals=yyy [ if filter] > event/trigger

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
 kernel/trace/trace.c             | 11 ++++--
 kernel/trace/trace_events_hist.c | 75 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 82 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f6fdda2..8109b89 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3788,12 +3788,17 @@ static const char readme_msg[] =
 #ifdef CONFIG_HIST_TRIGGERS
 	"      hist trigger\t- If set, event hits are aggregated into a hash table\n"
 	"\t    Format: hist:keys=<field1>\n"
+	"\t            [:values=<field1[,field2,...]]\n"
 	"\t            [:size=#entries]\n"
 	"\t            [if <filter>]\n\n"
 	"\t    When a matching event is hit, an entry is added to a hash\n"
-	"\t    table using the key named.  Keys correspond to fields in the\n"
-	"\t    event's format description.  On an event hit, the value of a\n"
-	"\t    sum called 'hitcount' is incremented, which is simply a count\n"
+	"\t    table using the key and value(s) named.  Keys and values\n"
+	"\t    correspond to fields in the event's format description.\n"
+	"\t    Values must correspond to numeric fields - on an event hit,\n"
+	"\t    the value(s) will be added to a sum kept for that field.\n"
+	"\t    The special string 'hitcount' can be used in place of an\n"
+	"\t    explicit value field - this is simply a count of event hits.\n"
+	"\t    If 'values' is not specified, 'hitcount' will be assumed.\n"
 	"\t    of event hits.  Keys can be any field.\n\n"
 	"\t    Reading the 'hist' file for the event will dump the hash\n"
 	"\t    table in its entirety to stdout.  Each printed hash table\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index ded348b..503df07 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -75,6 +75,7 @@ enum hist_field_flags {
 
 struct hist_trigger_attrs {
 	char		*keys_str;
+	char		*vals_str;
 	unsigned int	map_bits;
 };
 
@@ -155,6 +156,7 @@ static int parse_map_size(char *str)
 static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 {
 	kfree(attrs->keys_str);
+	kfree(attrs->vals_str);
 	kfree(attrs);
 }
 
@@ -173,6 +175,10 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
 		if (!strncmp(str, "keys", strlen("keys")) ||
 		    !strncmp(str, "key", strlen("key")))
 			attrs->keys_str = kstrdup(str, GFP_KERNEL);
+		else if (!strncmp(str, "values", strlen("values")) ||
+			 !strncmp(str, "vals", strlen("vals")) ||
+			 !strncmp(str, "val", strlen("val")))
+			attrs->vals_str = kstrdup(str, GFP_KERNEL);
 		else if (!strncmp(str, "size", strlen("size"))) {
 			int map_bits = parse_map_size(str);
 
@@ -256,13 +262,66 @@ static int create_hitcount_val(struct hist_trigger_data *hist_data)
 	return 0;
 }
 
+static int create_val_field(struct hist_trigger_data *hist_data,
+			    unsigned int val_idx,
+			    struct trace_event_file *file,
+			    char *field_str)
+{
+	struct ftrace_event_field *field = NULL;
+	unsigned long flags = 0;
+	int ret = 0;
+
+	field = trace_find_event_field(file->event_call, field_str);
+	if (!field) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	hist_data->fields[val_idx] = create_hist_field(field, flags);
+	if (!hist_data->fields[val_idx]) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	hist_data->n_vals++;
+ out:
+	return ret;
+}
+
 static int create_val_fields(struct hist_trigger_data *hist_data,
 			     struct trace_event_file *file)
 {
+	unsigned int vals_max = TRACING_MAP_FIELDS_MAX - TRACING_MAP_KEYS_MAX;
+	char *fields_str, *field_str;
+	unsigned int i, j;
 	int ret;
 
 	ret = create_hitcount_val(hist_data);
+	if (ret)
+		goto out;
 
+	fields_str = hist_data->attrs->vals_str;
+	if (!fields_str)
+		goto out;
+
+	strsep(&fields_str, "=");
+	if (!fields_str)
+		goto out;
+
+	vals_max = TRACING_MAP_FIELDS_MAX - TRACING_MAP_KEYS_MAX;
+
+	for (i = 0, j = 1; i < vals_max; i++) {
+		field_str = strsep(&fields_str, ",");
+		if (!field_str)
+			break;
+		if (!strcmp(field_str, "hitcount"))
+			continue;
+		ret = create_val_field(hist_data, j++, file, field_str);
+		if (ret)
+			goto out;
+	}
+	if (fields_str)
+		ret = -EINVAL;
+ out:
 	return ret;
 }
 
@@ -534,6 +593,12 @@ hist_trigger_entry_print(struct seq_file *m,
 	seq_printf(m, " hitcount: %10llu",
 		   tracing_map_read_sum(elt, HITCOUNT_IDX));
 
+	for (i = 1; i < hist_data->n_vals; i++) {
+		seq_printf(m, "  %s: %10llu",
+			   hist_data->fields[i]->field->name,
+			   tracing_map_read_sum(elt, i));
+	}
+
 	seq_puts(m, "\n");
 }
 
@@ -641,7 +706,15 @@ static int event_hist_trigger_print(struct seq_file *m,
 	}
 
 	seq_puts(m, ":vals=");
-	seq_puts(m, "hitcount");
+
+	for (i = 0; i < hist_data->n_vals; i++) {
+		if (i == 0)
+			seq_puts(m, "hitcount");
+		else {
+			seq_puts(m, ",");
+			hist_field_print(m, hist_data->fields[i]);
+		}
+	}
 
 	seq_puts(m, ":sort=");
 	seq_puts(m, "hitcount");
-- 
1.9.3

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