[PATCH] run_task_queue(&tq_disk) only if we written data to disk

[Marcelo Tosatti]

Hi, 

This patch makes page_launder() do actual disk IO
(run_task_queue(&tq_disk)) only if IO was queued in the page freeing
loop.

If we freed enough clean pages without needing do to any disk IO, there is
no need to call run_task_queue(&tq_disk).

 
--- linux/mm/vmscan.c.orig      Mon Feb 19 20:46:23 2001
+++ linux/mm/vmscan.c   Mon Feb 19 20:47:21 2001
@@ -657,12 +657,13 @@
        }
 
        /*
-        * We have to make sure the data is actually written to
-        * the disk now, otherwise we'll never get enough clean
-        * pages and the system will keep queueing dirty pages
+        * If we written something to disk, we have to make sure the data
is 
+        * actually written to the disk now, otherwise we'll never get
enough
+        * clean pages and the system will keep queueing dirty pages
         * for flushing.
         */
-       run_task_queue(&tq_disk);
+       if (launder_loop)
+               run_task_queue(&tq_disk);
 
        /*
         * Return the amount of pages we freed or made freeable.