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Re: User concurrency thresholding: where do I look?

From: "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)Sun(dot)COM>
To: "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)Sun(dot)COM>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-performance(at)postgresql(dot)org, Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Subject: Re: User concurrency thresholding: where do I look?
Date: 2007-07-27 20:04:57
Message-ID: 46AA4FE9.2030302@sun.com (view raw or flat)
Thread:
Lists: pgsql-performance
Using CLOG Buffers 32 and the commit sibling check patch I still see a 
drop at 1200-1300 users..



bash-3.00# ./4_lwlock_waits.d 18250

             Lock Id            Mode           Count
          XidGenLock          Shared               1
     CLogControlLock          Shared               2
       ProcArrayLock          Shared               2
          XidGenLock       Exclusive               4
     CLogControlLock       Exclusive              15
       WALInsertLock       Exclusive              18
        WALWriteLock       Exclusive              38
       ProcArrayLock       Exclusive              77

             Lock Id            Mode   Combined Time (ns)
          XidGenLock          Shared                88700
       WALInsertLock       Exclusive             69556000
       ProcArrayLock          Shared             95656800
          XidGenLock       Exclusive            139634100
     CLogControlLock       Exclusive            148822200
     CLogControlLock          Shared            161630000
        WALWriteLock       Exclusive            332781800
       ProcArrayLock       Exclusive           5688265500

bash-3.00# ./4_lwlock_waits.d 18599

             Lock Id            Mode           Count
       ProcArrayLock          Shared               2
          XidGenLock       Exclusive               3
          XidGenLock          Shared               4
     CLogControlLock          Shared               5
       WALInsertLock       Exclusive              10
     CLogControlLock       Exclusive              21
        WALWriteLock       Exclusive              28
       ProcArrayLock       Exclusive              54

             Lock Id            Mode   Combined Time (ns)
          XidGenLock       Exclusive              5688800
       WALInsertLock       Exclusive             11424700
     CLogControlLock          Shared             55589100
       ProcArrayLock          Shared            135220400
        WALWriteLock       Exclusive            177906900
          XidGenLock          Shared            524146500
     CLogControlLock       Exclusive            524563900
       ProcArrayLock       Exclusive           5828744500

bash-3.00#
bash-3.00# ./6_lwlock_stack.d 4 18599

             Lock Id            Mode           Count
       ProcArrayLock          Shared               1
       ProcArrayLock       Exclusive              52

             Lock Id            Mode   Combined Time (ns)
       ProcArrayLock          Shared             41428300
       ProcArrayLock       Exclusive           3858386500

             Lock Id   Combined Time (ns)


              postgres`LWLockAcquire+0x1f0
              postgres`GetSnapshotData+0x120
              postgres`GetTransactionSnapshot+0x80
              postgres`PortalStart+0x198
              postgres`exec_bind_message+0x84c
              postgres`PostgresMain+0x17f8
              postgres`BackendRun+0x2f8
              postgres`ServerLoop+0x680
              postgres`PostmasterMain+0xda8
              postgres`main+0x3d0
              postgres`_start+0x17c
  Shared                                                     41428300

              postgres`LWLockAcquire+0x1f0
              postgres`CommitTransaction+0x104
              postgres`CommitTransactionCommand+0xbc
              postgres`finish_xact_command+0x78
              postgres`exec_execute_message+0x42c
              postgres`PostgresMain+0x1838
              postgres`BackendRun+0x2f8
              postgres`ServerLoop+0x680
              postgres`PostmasterMain+0xda8
              postgres`main+0x3d0
              postgres`_start+0x17c
  Exclusive                                                3858386500


-Jignesh


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