diff --git a/sub/osd.c b/sub/osd.c
index a3da1dd3ca..6a57574a52 100644
--- a/sub/osd.c
+++ b/sub/osd.c
@@ -333,6 +333,8 @@ struct sub_bitmap_list *osd_render(struct osd_state *osd, struct mp_osd_res res,
 {
     mp_mutex_lock(&osd->lock);
 
+    int64_t start_time = mp_time_ns();
+
     struct sub_bitmap_list *list = talloc_zero(NULL, struct sub_bitmap_list);
     list->change_id = 1;
     list->w = res.w;
@@ -388,6 +390,11 @@ struct sub_bitmap_list *osd_render(struct osd_state *osd, struct mp_osd_res res,
     if (!(draw_flags & OSD_DRAW_SUB_FILTER))
         osd->want_redraw_notification = false;
 
+    double elapsed = MP_TIME_NS_TO_MS(mp_time_ns() - start_time);
+    bool slow = elapsed > 5;
+    mp_msg(osd->log, slow ? MSGL_DEBUG : MSGL_TRACE, "Spent %.3f ms in %s%s\n",
+           elapsed, __func__, slow ? " (slow!)" : "");
+
     mp_mutex_unlock(&osd->lock);
     return list;
 }