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Re: LWlock:LockManager waits - Mailing list pgsql-performance

From Luiz Fernando G. Verona
Subject Re: LWlock:LockManager waits
Date
Msg-id CAOnodNFh_C=2_KsQo==wocvGOzaUt4nEAON8ph=GShicbJeo7Q@mail.gmail.com
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In response to [MASSMAIL]LWlock:LockManager waits  (James Pang <jamespang886@gmail.com>)
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Hi James,

Take a look here, in the links you will find many info and real examples for LockManager issues.


Luiz

On Tue, Apr 9, 2024 at 4:08 AM James Pang <jamespang886@gmail.com> wrote:
   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

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