RE: Big Performance drop of Exceptions in UDFs between V11.2 and 13.4

   >  -----Original Message-----
   >  From: Tom Lane <tgl@sss.pgh.pa.us>
   >  Sent: Sunday, August 22, 2021 13:51
   >  To: Justin Pryzby <pryzby@telsasoft.com>
   >  Cc: Ranier Vilela <ranier.vf@gmail.com>; ldh@laurent-hasson.com;
   >  pgsql-performance@postgresql.org
   >  Subject: Re: Big Performance drop of Exceptions in UDFs between V11.2
   >  and 13.4
   >
   >  Justin Pryzby <pryzby@telsasoft.com> writes:
   >  > This looks useful, thanks.  It seems like maybe win64 builds are very
   >  > slow running this:
   >
   >  > exec_stmt_block() /
   >  > BeginInternalSubTransaction() /
   >  > AbortSubTransaction() /
   >  > reschedule_timeouts() /
   >  > schedule_alarm() /
   >  > setitimer() /
   >  > pg_timer_thread() /
   >  > WaitForSingleObjectEx ()
   >
   >  Hmm ... we should not be there unless there are active timeout events,
   >  which there aren't by default.  I wonder whether either Ranier or
   >  Laurent have statement_timeout or some similar option enabled.
   >
   >  I tried setting statement_timeout = '1 min' just to see if that would affect
   >  the results.  It does, but only incrementally on my Linux box (on v13, the
   >  exception-causing query slows from ~13sec to ~14sec).  It's possible that
   >  our Windows version of
   >  setitimer() is far slower, but that doesn't make a lot of sense really --- the
   >  client side of that just briefly takes a critical section.  It shouldn't be
   >  blocking.
   >
   >  Also, the Windows version (src/backend/port/win32/timer.c) hasn't
   >  changed at all since before v11.  So even if it's slow, that doesn't tell us
   >  what changed.
   >
   >  There is a patch in v14 (09cf1d522) that drastically reduces the rate at
   >  which we make setitimer() calls, which would likely be enough to fix any
   >  performance problem that may exist here.
   >  But it's still unclear what's different between v11 and v13.
   >
   >              regards, tom lane


Hello Tom,

On both my clean 13.4 install and current 11.2 install, I have
#statement_timeout = 0            # in milliseconds, 0 is disabled

Note that the 13.4 clean install I gave last measurements for has all stock settings.

Thank you,
Laurent.