Horton

LWlock:LockManager waits

James Pang <jamespang886@gmail.com>

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From: James Pang <jamespang886@gmail.com>
To: pgsql-performance@lists.postgresql.org
Date: 2024-04-09T03:07:49Z
Lists: pgsql-performance 
   we found sometimes , with many sessions running same query "select ..."
at the same time, saw many sessions waiting on "LockManager".  for example,
pg_stat_activity show.  It's a production server, so no enable
trace_lwlocks flag. could you direct me what's the possible reason and how
to reduce this "lockmanager" lock?  all the sql statement are "select " ,no
DML.

   time                                             wait_event
 count(pid)
2024-04-08 09:00:06.043996+00 | DataFileRead  |    42
 2024-04-08 09:00:06.043996+00 |               |    15
 2024-04-08 09:00:06.043996+00 | LockManager   |    31
 2024-04-08 09:00:06.043996+00 | BufferMapping |    46
 2024-04-08 09:00:07.114015+00 | LockManager   |    43
 2024-04-08 09:00:07.114015+00 | DataFileRead  |    28
 2024-04-08 09:00:07.114015+00 | ClientRead    |    11
 2024-04-08 09:00:07.114015+00 |               |    11

Thanks,

James