linux-kernel - Re: la la la la ... swappiness

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Date:	Mon, 4 Dec 2006 10:06:56 -0800
From:	Andrew Morton <akpm@...l.org>
To:	"Horst H. von Brand" <vonbrand@....utfsm.cl>
Cc:	Aucoin@...ston.RR.com, "'Kyle Moffett'" <mrmacman_g4@....com>,
	"'Tim Schmielau'" <tim@...sik3.uni-rostock.de>, torvalds@...l.org,
	linux-kernel@...r.kernel.org, clameter@....com
Subject: Re: la la la la ... swappiness

On Mon, 04 Dec 2006 14:07:22 -0300
"Horst H. von Brand" <vonbrand@....utfsm.cl> wrote:

> Please explain again:
> 
> - What you are doing, step by step

That 2GB machine apparently has a 1.6GB shm segment which is mlocked.  That will
cause the VM to do one heck of a lot of pointless scanning and could, I guess,
cause false oom decisions.  It's also an ia32 highmem machine, which adds to the
fun.

We could scan more:

--- a/mm/vmscan.c~a
+++ a/mm/vmscan.c
@@ -918,6 +918,7 @@ static unsigned long shrink_zone(int pri
 	 * slowly sift through the active list.
 	 */
 	zone->nr_scan_active += (zone->nr_active >> priority) + 1;
+	zone->nr_scan_active *= 2;
 	nr_active = zone->nr_scan_active;
 	if (nr_active >= sc->swap_cluster_max)
 		zone->nr_scan_active = 0;
@@ -925,6 +926,7 @@ static unsigned long shrink_zone(int pri
 		nr_active = 0;

 	zone->nr_scan_inactive += (zone->nr_inactive >> priority) + 1;
+	zone->nr_scan_inactive *= 2;
 	nr_inactive = zone->nr_scan_inactive;
 	if (nr_inactive >= sc->swap_cluster_max)
 		zone->nr_scan_inactive = 0;
_

but that's rather dumb.  Better would be to remove mlocked pages from the
LRU.
-
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