Re: PostgreSQL 8.0.6 crash

On Fri, Feb 10, 2006 at 10:01:18AM -0600, Jim C. Nasby wrote:
> BTW, I was shocked when I found out that FreeBSD actually has an OOM
> killer itself. Yet I've never heard of anyone having problems with it.
> Granted, the FreeBSD OOM could be better designed to pick the right
> process to kill, but I'd bet that the real reason you never hear about
> it is because FreeBSD admins are clued enough to a) setup a reasonable
> amount of swap and b) do a better job of monitoring memory usage so that
> you don't start swapping in the first place.

Hmm, I do wonder what FreeBSDs overcommit policy is. For example on my
computer right now the total allocated VM is approximately 3 times the
actual memory in the computer and about twice if you include swap. By a
strict policy of overcommit my computer wouldn't complete the boot
sequence, whereas as currently it runs without using any swap.

Disabling overcommit has a serious cost in that most of your VM will
never be used. Are people really suggesting that I can't run a few
daemons, X and a web-browser on FreeBSD without allocating 3 times my
physical memory in swap?

However, my real question is: while trying to find info about FreeBSDs
overcommit policy, I just get lot of people complaining about freebsd
killing random processes. Does anyone know a site that describes how it
works? I understand Linux's overcommit policy just fine.

Disclaimer: The Linux OOM killer has never killed the wrong process for
me, so I don't have any bad experiences with overcommit.

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.