tracing: Add hist trigger support for user-defined sorting ('sort=' param)

Allow users to specify keys and/or values to sort on.  With this
addition, keys and values specified using the 'keys=' and 'vals='
keywords can be used to sort the hist trigger output via a new 'sort='
keyword.  If multiple sort keys are specified, the output will be
sorted using the second key as a secondary sort key, etc.  The default
sort order is ascending; if the user wants a different sort order,
'.descending' can be appended to the specific sort key.  Before this
addition, output was always sorted by 'hitcount' in ascending order.

This expands the hist trigger syntax from this:

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

to this:

    # echo hist:keys=xxx:vals=yyy:sort=zzz.descending \
          [ if filter] > event/trigger

Link: http://lkml.kernel.org/r/b30a41db66ba486979c4f987aff5fab500ea53b3.1457029949.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 109 insertions, 3 deletions

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 65fdfc6cb633..03ba4530c08c 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -85,6 +85,7 @@ enum hist_field_flags {
 struct hist_trigger_attrs {
 	char		*keys_str;
 	char		*vals_str;
+	char		*sort_key_str;
 	unsigned int	map_bits;
 };
 
@@ -165,6 +166,7 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 	if (!attrs)
 		return;
 
+	kfree(attrs->sort_key_str);
 	kfree(attrs->keys_str);
 	kfree(attrs->vals_str);
 	kfree(attrs);
@@ -189,6 +191,8 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
 			 (strncmp(str, "vals=", strlen("vals=")) == 0) ||
 			 (strncmp(str, "values=", strlen("values=")) == 0))
 			attrs->vals_str = kstrdup(str, GFP_KERNEL);
+		else if (strncmp(str, "sort=", strlen("sort=")) == 0)
+			attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
 		else if (strncmp(str, "size=", strlen("size=")) == 0) {
 			int map_bits = parse_map_size(str);
 
@@ -450,12 +454,92 @@ static int create_hist_fields(struct hist_trigger_data *hist_data,
 	return ret;
 }
 
+static int is_descending(const char *str)
+{
+	if (!str)
+		return 0;
+
+	if (strcmp(str, "descending") == 0)
+		return 1;
+
+	if (strcmp(str, "ascending") == 0)
+		return 0;
+
+	return -EINVAL;
+}
+
 static int create_sort_keys(struct hist_trigger_data *hist_data)
 {
-	int ret = 0;
+	char *fields_str = hist_data->attrs->sort_key_str;
+	struct ftrace_event_field *field = NULL;
+	struct tracing_map_sort_key *sort_key;
+	int descending, ret = 0;
+	unsigned int i, j;
+
+	hist_data->n_sort_keys = 1; /* we always have at least one, hitcount */
+
+	if (!fields_str)
+		goto out;
+
+	strsep(&fields_str, "=");
+	if (!fields_str) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
+		char *field_str, *field_name;
+
+		sort_key = &hist_data->sort_keys[i];
+
+		field_str = strsep(&fields_str, ",");
+		if (!field_str) {
+			if (i == 0)
+				ret = -EINVAL;
+			break;
+		}
+
+		if ((i == TRACING_MAP_SORT_KEYS_MAX - 1) && fields_str) {
+			ret = -EINVAL;
+			break;
+		}
 
-	hist_data->n_sort_keys = 1; /* sort_keys[0] is always hitcount */
+		field_name = strsep(&field_str, ".");
+		if (!field_name) {
+			ret = -EINVAL;
+			break;
+		}
+
+		if (strcmp(field_name, "hitcount") == 0) {
+			descending = is_descending(field_str);
+			if (descending < 0) {
+				ret = descending;
+				break;
+			}
+			sort_key->descending = descending;
+			continue;
+		}
 
+		for (j = 1; j < hist_data->n_fields; j++) {
+			field = hist_data->fields[j]->field;
+			if (field && (strcmp(field_name, field->name) == 0)) {
+				sort_key->field_idx = j;
+				descending = is_descending(field_str);
+				if (descending < 0) {
+					ret = descending;
+					goto out;
+				}
+				sort_key->descending = descending;
+				break;
+			}
+		}
+		if (j == hist_data->n_fields) {
+			ret = -EINVAL;
+			break;
+		}
+	}
+	hist_data->n_sort_keys = i;
+ out:
 	return ret;
 }
 
@@ -758,7 +842,29 @@ static int event_hist_trigger_print(struct seq_file *m,
 	}
 
 	seq_puts(m, ":sort=");
-	seq_puts(m, "hitcount");
+
+	for (i = 0; i < hist_data->n_sort_keys; i++) {
+		struct tracing_map_sort_key *sort_key;
+
+		sort_key = &hist_data->sort_keys[i];
+
+		if (i > 0)
+			seq_puts(m, ",");
+
+		if (sort_key->field_idx == HITCOUNT_IDX)
+			seq_puts(m, "hitcount");
+		else {
+			unsigned int idx = sort_key->field_idx;
+
+			if (WARN_ON(idx >= TRACING_MAP_FIELDS_MAX))
+				return -EINVAL;
+
+			hist_field_print(m, hist_data->fields[idx]);
+		}
+
+		if (sort_key->descending)
+			seq_puts(m, ".descending");
+	}
 
 	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));