Re: pg_stat_activity.waiting_start

On Mon, Dec 26, 2016 at 03:36:39PM -0500, Tom Lane wrote:
> In practice, there should never be waits on LWLocks (much less spinlocks)
> that exceed order-of-milliseconds; if there are, either we chose the wrong
> lock type or the system is pretty broken in general. So maybe it's
> sufficient if we provide a wait start time for heavyweight locks ...
> though that still seems kind of ugly. (Also, I don't recall the existing
> code factorization there, but getting the start time into pg_stat_activity
> without an extra gettimeofday call might be hard. As I said, there is
> one being done, but I'm not sure how accessible its result is.)

Agreed. No need in adding overhead for short-lived locks because the
milli-second values are going to be meaningless to users. I would be
happy if we could find some weasel value for non-heavyweight locks.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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