Re: [RFC] changes to buffer.c (was Test12 ll_rw_block error)

[Chris Mason <mason@suse.com>]

On Thursday, December 28, 2000 16:49:14 +0100 Daniel Phillips <phillips@innominate.de> wrote:

[ dbench 48 test on the anon space mapping patch ]

> 
> This benchmark doesn't seem to suffer a lot from noise, so the 7%
> slowdown with your patch likely real.
> 

Ok, page_launder is supposed to run through the inactive dirty
list twice, and on the second run, it wants to start i/o.  But,
if the page is dirty, writepage is called on the first run.  With
my patch, this flushes lots more data than it used to.  

I have writepage doing all the i/o, and try_to_free_buffers
only waits on it.  This diff makes it so writepage is only called
on the second loop through the inactive dirty list, could you 
please give it a try (slightly faster in my tests).

Linus and Rik are cc'd in to find out if this is a good idea in
general.

-chris

--- linux-test13-pre4/mm/vmscan.c	Sat Dec 23 13:14:26 2000
+++ linux/mm/vmscan.c	Thu Dec 28 15:02:08 2000
@@ -609,7 +609,7 @@
 				goto page_active;
 
 			/* Can't start IO? Move it to the back of the list */
-			if (!can_get_io_locks) {
+			if (!launder_loop || !can_get_io_locks) {
 				list_del(page_lru);
 				list_add(page_lru, &inactive_dirty_list);
 				UnlockPage(page);

-
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