1 files changed, 21 insertions, 15 deletions

diff --git a/source/blender/blenlib/intern/task.c b/source/blender/blenlib/intern/task.c
index 2f6c88c128a..6cdaec97d9a 100644
--- a/source/blender/blenlib/intern/task.c
+++ b/source/blender/blenlib/intern/task.c
@@ -1064,22 +1064,28 @@ BLI_INLINE void task_parallel_range_calc_chunk_size(const TaskParallelSettings *
     chunk_size = settings->min_iter_per_thread;
   }
   else {
-    /* Basic heuristic to avoid threading on low amount of items. We could make that limit
-     * configurable in settings too... */
-    if (tot_items > 0 && tot_items < 256) {
-      chunk_size = tot_items;
-    }
-    /* NOTE: The idea here is to compensate for rather measurable threading
+    /* Multiplier used in heuristics below to define "optimal" chunk size.
+     * The idea here is to increase the chunk size to compensate for a rather measurable threading
      * overhead caused by fetching tasks. With too many CPU threads we are starting
-     * to spend too much time in those overheads. */
-    else if (num_tasks > 32) {
-      chunk_size = 128;
-    }
-    else if (num_tasks > 16) {
-      chunk_size = 64;
-    }
-    else {
-      chunk_size = 32;
+     * to spend too much time in those overheads.
+     * First values are: 1 if num_tasks < 16;
+     *              else 2 if num_tasks < 32;
+     *              else 3 if num_tasks < 48;
+     *              else 4 if num_tasks < 64;
+     *                   etc.
+     * Note: If we wanted to keep the 'power of two' multiplier, we'd need something like:
+     *     1 << max_ii(0, (int)(sizeof(int) * 8) - 1 - bitscan_reverse_i(num_tasks) - 3)
+     */
+    const int num_tasks_factor = max_ii(1, num_tasks >> 3);
+
+    /* We could make that 'base' 32 number configurable in TaskParallelSettings too, or maybe just
+     * always use that heuristic using TaskParallelSettings.min_iter_per_thread as basis? */
+    chunk_size = 32 * num_tasks_factor;
+
+    /* Basic heuristic to avoid threading on low amount of items.
+     * We could make that limit configurable in settings too. */
+    if (tot_items > 0 && tot_items < max_ii(256, chunk_size * 2)) {
+      chunk_size = tot_items;
     }
   }