new approximation for merged peak stats

Author: artem-lunarg

src/stats.c

@@ -86,11 +86,11 @@ void _mi_stat_adjust_decrease(mi_stat_count_t* stat, size_t amount) {
 static void mi_stat_count_add_mt(mi_stat_count_t* stat, const mi_stat_count_t* src) {
   if (stat==src) return;
   mi_atomic_void_addi64_relaxed(&stat->total, &src->total); 
-  mi_atomic_void_addi64_relaxed(&stat->current, &src->current); 
-  // peak scores do really not work across threads .. we just add them
-  mi_atomic_void_addi64_relaxed( &stat->peak, &src->peak);
-  // or, take the max?
-  // mi_atomic_maxi64_relaxed(&stat->peak, src->peak);
+  
+  int64_t prev_current = mi_atomic_addi64_relaxed(&stat->current, src->current);
+
+  // global current plus thread peak approximates new global peak
+  mi_atomic_maxi64_relaxed(&stat->peak, prev_current + src->peak);
 }
 
 static void mi_stat_counter_add_mt(mi_stat_counter_t* stat, const mi_stat_counter_t* src) {