Re: RFC: replace pg_stat_activity.waiting with something more descriptive

From: Peter Geoghegan <pg(at)heroku(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Peter Eisentraut <peter_e(at)gmx(dot)net>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: RFC: replace pg_stat_activity.waiting with something more descriptive
Date: 2015-07-17 02:03:33
Message-ID: CAM3SWZRwo6i0gminoLugvfsnuBksdXuBW60wwHf_QXxsC-Xv0w@mail.gmail.com
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On Tue, Jul 14, 2015 at 7:25 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> FWIW, I entirely share Robert's opinion that adding gettimeofday()
> overhead in routinely-taken paths is likely not to be acceptable.

I think that it can depend on many factors. For example, the
availability of vDSO support on Linux/glibc.

I've heard that clock_gettime() with CLOCK_REALTIME_COARSE, or with
CLOCK_MONOTONIC_COARSE can have significantly lower overhead than
gettimeofday().
--
Peter Geoghegan

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