[PATCH v4 16/20] libtraceeval histogram: Use stack for old copy in update

[Steven Rostedt <rostedt@xxxxxxxxxxx>]

From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

In the update, instead of using the heap, use the stack to save the old
values. This should save time where it does not need to allocate and then
free the value list to do an update.

Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 src/histograms.c | 51 ++++++++++++++++++++++++++++++++++++------------
 1 file changed, 38 insertions(+), 13 deletions(-)

diff --git a/src/histograms.c b/src/histograms.c
index 185480cabad2..e6a15a25bba0 100644
--- a/src/histograms.c
+++ b/src/histograms.c
@@ -597,17 +597,23 @@ static int copy_traceeval_data(struct traceeval_type *type,
  *
  * Does not call the release() callback if a copy() exists.
  */
-static void data_release(size_t size, union traceeval_data **data,
-				struct traceeval_type *type)
+static void data_release(size_t size, union traceeval_data *data,
+			 struct traceeval_type *type)
 {
 	for (size_t i = 0; i < size; i++) {
 		/* A copy should handle releases */
 		if (type[i].release && !type[i].copy)
-			type[i].release(&type[i], &(*data)[i]);
+			type[i].release(&type[i], &data[i]);
 
 		if (type[i].type == TRACEEVAL_TYPE_STRING)
-			free((*data)[i].string);
+			free(data[i].string);
 	}
+}
+
+static void data_release_and_free(size_t size, union traceeval_data **data,
+				struct traceeval_type *type)
+{
+	data_release(size, *data, type);
 	free(*data);
 	*data = NULL;
 }
@@ -641,7 +647,7 @@ static int dup_traceeval_data_set(size_t size, struct traceeval_type *type,
 	return 1;
 
 fail:
-	data_release(i, copy, type);
+	data_release_and_free(i, copy, type);
 	return -1;
 }
 
@@ -700,7 +706,7 @@ void traceeval_results_release(struct traceeval *teval,
 		return;
 	}
 
-	data_release(teval->nr_val_types, &results, teval->val_types);
+	data_release_and_free(teval->nr_val_types, &results, teval->val_types);
 }
 
 static struct entry *create_hist_entry(struct traceeval *teval,
@@ -756,7 +762,7 @@ static int create_entry(struct traceeval *teval,
 	return 0;
 
 fail:
-	data_release(teval->nr_key_types, &new_keys, teval->key_types);
+	data_release_and_free(teval->nr_key_types, &new_keys, teval->key_types);
 
 fail_stats:
 	free(entry->val_stats);
@@ -776,15 +782,34 @@ fail_entry:
 static int update_entry(struct traceeval *teval, struct entry *entry,
 			const union traceeval_data *vals)
 {
-	union traceeval_data *new_vals;
+	struct traceeval_stat *stats = entry->val_stats;
+	struct traceeval_type *types = teval->val_types;
+	union traceeval_data *copy = entry->vals;
+	union traceeval_data old[teval->nr_val_types];
+	size_t size = teval->nr_val_types;
+	size_t i;
 
-	if (dup_traceeval_data_set(teval->nr_val_types, teval->val_types,
-				   entry->val_stats, vals, &new_vals) == -1)
-		return -1;
+	if (!size)
+		return 0;
 
-	clean_data_set(entry->vals, teval->val_types, teval->nr_val_types);
-	entry->vals = new_vals;
+	for (i = 0; i < size; i++) {
+		old[i] = copy[i];
+
+		if (copy_traceeval_data(types + i, stats + i,
+					copy + i, vals + i))
+			goto fail;
+	}
+	data_release(size, old, types);
 	return 0;
+ fail:
+	/* Free the new values that were added */
+	data_release(i, copy, types);
+	/* Put back the old values */
+	for (i--; i >= 0; i--) {
+		copy_traceeval_data(types + i, NULL,
+				    copy + i, old + i);
+	}
+	return -1;
 }
 
 struct traceeval_stat *traceeval_stat(struct traceeval *teval,
-- 
2.40.1