Re: Timing of 'SELECT 1'

Andreas Pflug wrote:
> Bruce Momjian wrote:
>
> >>There seems to be a 'PostgreSQL ping' time of about 1-2 ms in best case
> >>conditions which limits the amount of queries you can fire off in 1
> >>second, no matter how simple. In certain rare cases this is something
> >>of a bottleneck. In my personal case it would be nice to see that time
> >>lower because converted COBOL applications tend to generate a lot of
> >>'simple' queries.
> >>
> >>
> >
> >Yes, most of that might be network time. I am using log_duration, which
> >I think just tests backend time, not network transfer time, but I might
> >be wrong. I want to look into this as it seems no one knows the answer.
> >
> >
> >
> That's easy to verify with standard ping. In my switched 100MBit
> network, roundtrip for small packets is about 0.2 ms, and 0.5ms for 1kb
> packets. How about context switch latency?

I am on a dual Xeon. I wouldn't think there was that much of a context
switch overhead, except for kernel calls.

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