Re: Occasional giant spikes in CPU load

Craig James <craig_james@emolecules.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
justa 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 -
itshows 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