Re: Queries intermittently slow - Mailing list pgsql-performance

>
>So what seems more likely after more thought is that the pages are staying
>in our shared buffer arena just fine, but the kernel is randomly choosing
>to swap out parts of the arena, and the delays correspond to swap-in
>waits.  (There would still have to be a mighty crummy disk subsystem
>underlying things for swap-in to take so long, but this is a more
>plausible theory for exactly what's invoking the disk read.)
>
>Postgres can't directly see when this is happening, but you could try
>watching "iostat 1" and noticing whether swap-in events seem to be
>correlated with the slow queries.
>
>If this is the problem, then the answer is to reduce the pressure on
>system memory so that swap-outs are less likely.  You might find that
>a smaller shared_buffer arena is a good thing (so that all of it stays
>"hot" and unswappable from the kernel's perspective).  Or reduce the
>number of active backend processes.
>
>regards, tom lane

One change to my setup that my server guy pointed out - this database server is *not* a cloud server, but in fact a
physicalDell box with SSDs.  So unless something is majorly wrong with our disk setup, disk IO should not be a factor.
 

I also checked and the box is not swapping at all.

I guess we’re back to lock contention?

Thanks,
Scott
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