Re: heavy swapping, not sure why

On Mon, Aug 29, 2011 at 5:01 PM, Alan Hodgson <ahodgson@simkin.ca> wrote:
> On August 29, 2011 02:34:26 PM you wrote:
>> On Mon, Aug 29, 2011 at 3:46 PM, Alan Hodgson <ahodgson@simkin.ca> wrote:
>> > On August 29, 2011 01:36:07 PM Lonni J Friedman wrote:
>> >> I have several Linux-x68_64 based dedicated PostgreSQL servers where
>> >> I'm experiencing significant swap usage growth over time.
>> >
>> > It's the Linux kernel that does it, not PostgreSQL. Set vm.swappiness=0
>> > (usually in /etc/sysctl.conf) and put that into effect.
>>
>> that won't help and, in almost all cases, is a bad idea.
>
> Overly aggressive swapping with the default settings has frequently caused me
> performance issues. Using this prevents those problems.

On a machine with lots of memory, I've run into pathological behaviour
with both the RHEL 5 and Ubuntu 10.04 kernels where the kswapd starts
eating up CPU and swap io like mad, while doing essentially nothing.
Setting swappiness to 0 delayed this behaviour but did not stop it.
Given that I'm on a machine with 128G ram, I just put "/sbin/swapoff
-a" in /etc/rc.local and viola, problem solved.