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Re: heavy swapping, not sure why

From: Allan Kamau <kamauallan(at)gmail(dot)com>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: heavy swapping, not sure why
Date: 2011-08-30 08:05:09
Message-ID: CAF3N6oTsY+fNyViZEmt8n66t5-HFkzEQW0KM0LbQDdVKoycyQw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-general
On Tue, Aug 30, 2011 at 10:39 AM, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> wrote:
> On Tue, Aug 30, 2011 at 12:54 AM, Florian Weimer <fweimer(at)bfk(dot)de> wrote:
>> * Scott Marlowe:
>>
>>> 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.
>>
>> Was this NUMA machine?  Some older kernels can only migrate pages
>> between nodes through swap.
>
> 48 core AMD Magny Cours.  I also had to turn off  zone reclaim mode on
> it or it would slow to a crawl as the OS started to cache more and
> more data.
>
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I have experienced such behaviour on Ubuntu 64bit OS but not on Fedora
64bit OS. Try installing Fedora on a test machine and see if you run
into the high memory consumption problem(s).

Allan.

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