linux-kernel - RE: la la la la ... swappiness

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Date:	Sun, 3 Dec 2006 00:18:26 -0600
From:	"Aucoin" <Aucoin@...ston.RR.com>
To:	<akpm@...l.org>, <torvalds@...l.org>,
	<linux-kernel@...r.kernel.org>, <clameter@....com>
Subject: RE: la la la la ... swappiness

Reformatted as plain text.

________________________________________
From: Aucoin [mailto:Aucoin@...ston.RR.com] 
Sent: Sunday, December 03, 2006 12:17 AM
To: 'akpm@...l.org'; 'torvalds@...l.org'; 'linux-kernel@...r.kernel.org';
'clameter@....com'
Subject: la la la la ... swappiness

I set swappiness to zero and it doesn't do what I want!

I have a system that runs as a Linux based data server 24x7 and occasionally
I need to apply an update or patch. It's a BIIIG patch to the tune of
several hundred megabytes, let's say 600MB for a good round number. The
server software itself runs on very tight memory boundaries, I've
preallocated a large chunk of memory that is shared amongst several
processes as a form of application cache, there is barely 15% spare memory
floating around.

The update is delivered to the server as a tar file. In order to minimize
down time I untar this update and verify the contents landed correctly
before switching over to the updated software.

The problem is when I attempt to untar the payload disk I/O starts caching,
the inactive page count reels wildly out of control, the system starts
swapping, OOM fires and there goes my 4 9's uptime. My system just suffered
a catastrophic failure because I can't control pagecache due to disk I/O.
I need a pagecache throttle, what do you suggest?

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