Re: Occasional giant spikes in CPU load

Craig James <craig_james(at)emolecules(dot)com> writes:
> Most of the time Postgres runs nicely, but two or three times a day we get a huge spike in the CPU load that lasts just a short time -- it jumps to 10-20 CPU loads. Today it hit 100 CPU loads. Sometimes days go by with no spike events. During these spikes, the system is completely unresponsive (you can't even login via ssh).
> I managed to capture one such event using top(1) with the "batch" option as a background process. See output below - it shows 19 active postgress processes, but I think it missed the bulk of the spike.

> Any ideas where I can look to find what's triggering this?

> Postgres 8.3.0
^^^^^

If it's really 8.3.0, try updating to 8.3.something-recent. We've fixed
a whole lot of bugs since then.

I have a suspicion that this might be an sinval overrun scenario, in
which case you'd need to update to 8.4 to get a real fix. But updating
in the 8.3 branch would be cheap and easy.

If it is sinval overrun, it would presumably be triggered by a whole lot
of catalog changes being made at approximately the same time. Can you
correlate the spikes with anything like that?

regards, tom lane