Re: System load consideration before spawning parallel workers

Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> As I just wrote in another message in this thread, I don't trust system
> load metrics very much as a gatekeeper.  They are reasonable for
> long-term charting to discover trends, but there are numerous potential
> problems for using them for this kind of resource control thing.

As a note in support of that, sendmail has a "feature" to suppress service
if system load gets above X, which I have never found to do anything
except result in self-DOSing.  The load spike might not have anything to
do with the service that is trying to un-spike things.  Even if it does,
Peter is correct to note that the response delay is much too long to form
part of a useful feedback loop.  It could be all right for scheduling
activities whose length is comparable to the load average measurement
interval, but not for short-term decisions.
        regards, tom lane