On Sat, Dec 24, 2016 at 7:46 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Stephen Frost <sfr...@snowman.net> writes: >> * Tom Lane (t...@sss.pgh.pa.us) wrote: >>> The difficulty with that is it'd require a gettimeofday() call for >>> every wait start. Even on platforms where those are relatively cheap, >>> the overhead would be nasty --- and on some platforms, it'd be >>> astonishingly bad. We sweated quite a lot to get the overhead of >>> pg_stat_activity wait monitoring down to the point where it would be >>> tolerable for non-heavyweight locks, but I'm afraid this would push >>> it back into the not-tolerable range. > >> Could we handle this like log_lock_waits..? > > Well, that only applies to heavyweight locks, which do a gettimeofday > anyway in order to schedule the deadlock-check timeout. If you were > willing to populate this new column only for heavyweight locks, maybe it > could be done for minimal overhead. But that would be backsliding > quite a lot compared to what we just did to extend pg_stat_activity's > coverage of lock types. >
Can we think of introducing new guc trace_system_waits or something like that which will indicate that the sessions will report the value of wait_start in pg_stat_activity? The default value of such a parameter can be false which means wait_start will be shown as NULL in pg_stat_activity and when it is enabled the wait_start can show the time as proposed in this thread. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
