Subject: Re: UBC on a no swap system
To: Vasant Kanchan <>
From: David Maxwell <>
List: tech-kern
Date: 06/18/2003 17:53:42
On Tue, Jun 17, 2003 at 11:37:55AM -0700, Vasant Kanchan wrote:
> Hi,
> I am running  NetBSD-1.6.1 on a  FLASH based system without a swap 
> partition.
> While running the system I monitor memory usage with top. Top shows 7Mb 
> for File
> which I assume is the buffer cache, 1.6M Free and 17M inactive. 
> Eventually system
> runs out of memory. The question I have is if the pageout daemon moves 
> pages from the
> UBC to free memory. Can I limit amout of pages in the cache ?

There are sysctl parameters to constrain caching:

Lowering these (as a percentage of available memory) will shrink the
maximum amount used for caching. Since the total of the three defaults
is over 100 (because, for a general purpose OS, we can't guess what the
workload will look like) you can see where you're hitting a problem.
Determine which you need to constrain in your application, and lower

vm.anonmax = 80
vm.execmax = 30
vm.filemax = 50

David Maxwell,| --> Although some of you out
there might find a microwave oven controlled by a Unix system an attractive
idea, controlling a microwave oven is easily accomplished with the smallest
of microcontrollers. - Russ Hersch - (Microcontroller primer and FAQ)