malloc_trim is itself very poor and gets slower and slower as the heap becomes

more fragmented. Run it only once an hour. GitHub issue 2551.

grid.c

@@ -265,9 +265,6 @@ grid_free_lines(struct grid *gd, u_int py, u_int ny)
 
 	for (yy = py; yy < py + ny; yy++)
 		grid_free_line(gd, yy);
-#ifdef HAVE_MALLOC_TRIM
-	malloc_trim(0);
-#endif
 }
 
 /* Create a new grid. */

server.c

@@ -159,6 +159,10 @@ server_tidy_event(__unused int fd, __unused short events, __unused void *data)
 
     format_tidy_jobs();
 
+#ifdef HAVE_MALLOC_TRIM
+    malloc_trim(0);
+#endif
+
     log_debug("%s: took %llu milliseconds", __func__, get_timer() - t);
     evtimer_add(&server_ev_tidy, &tv);
 }