[PATCH v8 10/23] tracing: Add hist trigger support for compound keys

[Tom Zanussi]

Allow users to specify multiple trace event fields to use in keys by
allowing multiple fields in the 'keys=' keyword.  With this addition,
any unique combination of any of the fields named in the 'keys'
keyword will result in a new entry being added to the hash table.

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
 kernel/trace/trace.c             |  8 +++++---
 kernel/trace/trace_events_hist.c | 40 ++++++++++++++++++++++++++++++----------
 2 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8109b89..1e4801e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3787,19 +3787,21 @@ static const char readme_msg[] =
 	"\t   Filters can be ignored when removing a trigger.\n"
 #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    Format: hist:keys=<field1>[,field2,...]\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 and value(s) named.  Keys and values\n"
+	"\t    table using the key(s) 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    of event hits.  Keys can be any field.  Compound keys\n"
+	"\t    consisting of up to two fields can be specified by the 'keys'\n"
+	"\t    keyword.\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"
 	"\t    entry is a simple list of the keys and values comprising the\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 503df07..3d5433a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -32,6 +32,7 @@ struct hist_field {
 	unsigned long			flags;
 	hist_field_fn_t			fn;
 	unsigned int			size;
+	unsigned int			offset;
 };
 
 static u64 hist_field_counter(struct hist_field *field, void *event)
@@ -64,8 +65,8 @@ DEFINE_HIST_FIELD_FN(s8);
 DEFINE_HIST_FIELD_FN(u8);
 
 #define HITCOUNT_IDX		0
-#define HIST_KEY_MAX		1
-#define HIST_KEY_SIZE_MAX	MAX_FILTER_STR_VAL
+#define HIST_KEY_MAX		2
+#define HIST_KEY_SIZE_MAX	(MAX_FILTER_STR_VAL + sizeof(u64))
 
 enum hist_field_flags {
 	HIST_FIELD_HITCOUNT	= 1,
@@ -327,6 +328,7 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
 
 static int create_key_field(struct hist_trigger_data *hist_data,
 			    unsigned int key_idx,
+			    unsigned int key_offset,
 			    struct trace_event_file *file,
 			    char *field_str)
 {
@@ -353,7 +355,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 
 	key_size = ALIGN(key_size, sizeof(u64));
 	hist_data->fields[key_idx]->size = key_size;
-	hist_data->key_size = key_size;
+	hist_data->fields[key_idx]->offset = key_offset;
+	hist_data->key_size += key_size;
 	if (hist_data->key_size > HIST_KEY_SIZE_MAX) {
 		ret = -EINVAL;
 		goto out;
@@ -368,7 +371,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 static int create_key_fields(struct hist_trigger_data *hist_data,
 			     struct trace_event_file *file)
 {
-	unsigned int i, n_vals = hist_data->n_vals;
+	unsigned int i, key_offset = 0, n_vals = hist_data->n_vals;
 	char *fields_str, *field_str;
 	int ret = -EINVAL;
 
@@ -384,9 +387,11 @@ static int create_key_fields(struct hist_trigger_data *hist_data,
 		field_str = strsep(&fields_str, ",");
 		if (!field_str)
 			break;
-		ret = create_key_field(hist_data, i, file, field_str);
+		ret = create_key_field(hist_data, i, key_offset,
+				       file, field_str);
 		if (ret < 0)
 			goto out;
+		key_offset += ret;
 	}
 	if (fields_str) {
 		ret = -EINVAL;
@@ -451,7 +456,10 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
 			else
 				cmp_fn = tracing_map_cmp_num(field->size,
 							     field->is_signed);
-			idx = tracing_map_add_key_field(map, 0, cmp_fn);
+			idx = tracing_map_add_key_field(map,
+							hist_field->offset,
+							cmp_fn);
+
 		} else
 			idx = tracing_map_add_sum_field(map);
 
@@ -531,6 +539,7 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
 static void event_hist_trigger(struct event_trigger_data *data, void *rec)
 {
 	struct hist_trigger_data *hist_data = data->private_data;
+	char compound_key[HIST_KEY_SIZE_MAX];
 	struct hist_field *key_field;
 	struct tracing_map_elt *elt;
 	u64 field_contents;
@@ -542,6 +551,9 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
 		return;
 	}
 
+	if (hist_data->n_keys > 1)
+		memset(compound_key, 0, hist_data->key_size);
+
 	for (i = hist_data->n_vals; i < hist_data->n_fields; i++) {
 		key_field = hist_data->fields[i];
 
@@ -550,8 +562,16 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
 			key = (void *)field_contents;
 		else
 			key = (void *)&field_contents;
+
+		if (hist_data->n_keys > 1) {
+			memcpy(compound_key + key_field->offset, key,
+			       key_field->size);
+		}
 	}
 
+	if (hist_data->n_keys > 1)
+		key = compound_key;
+
 	elt = tracing_map_insert(hist_data->map, key);
 	if (elt)
 		hist_trigger_elt_update(hist_data, elt, rec);
@@ -580,11 +600,11 @@ hist_trigger_entry_print(struct seq_file *m,
 
 		if (key_field->flags & HIST_FIELD_STRING) {
 			seq_printf(m, "%s: %-35s", key_field->field->name,
-				   (char *)key);
+				   (char *)(key + key_field->offset));
 		} else {
-			uval = *(u64 *)key;
-			seq_printf(m, "%s: %10llu",
-				   key_field->field->name, uval);
+			uval = *(u64 *)(key + key_field->offset);
+			seq_printf(m, "%s: %10llu", key_field->field->name,
+				   uval);
 		}
 	}
 
-- 
1.9.3

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