RE: la la la la ... swappiness

[Aucoin]

Reformatted as plain text.

________________________________________
From: Aucoin [mailto:Aucoin@xxxxxxxxxxxxxx] 
Sent: Sunday, December 03, 2006 12:17 AM
To: 'akpm@xxxxxxxx'; 'torvalds@xxxxxxxx'; 'linux-kernel@xxxxxxxxxxxxxxx';
'clameter@xxxxxxx'
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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