Re: User concurrency thresholding: where do I look?

От: Tom Lane
Тема: Re: User concurrency thresholding: where do I look?
Дата: ,
Msg-id: 12686.1184865938@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: User concurrency thresholding: where do I look?  (Josh Berkus)
Ответы: Re: User concurrency thresholding: where do I look?  (Alvaro Herrera)
Re: User concurrency thresholding: where do I look?  (Gregory Stark)
Список: pgsql-performance

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User concurrency thresholding: where do I look?  (Josh Berkus, )
 Re: User concurrency thresholding: where do I look?  ("Joshua D. Drake", )
 Re: User concurrency thresholding: where do I look?  (Alvaro Herrera, )
  Re: User concurrency thresholding: where do I look?  (Josh Berkus, )
   Re: User concurrency thresholding: where do I look?  (Tom Lane, )
    Re: User concurrency thresholding: where do I look?  (Alvaro Herrera, )
     Re: User concurrency thresholding: where do I look?  (Tom Lane, )
      Re: User concurrency thresholding: where do I look?  (Josh Berkus, )
       Re: User concurrency thresholding: where do I look?  (Tom Lane, )
        Re: User concurrency thresholding: where do I look?  (Josh Berkus, )
         Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
          Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
          Re: User concurrency thresholding: where do I look?  (Tom Lane, )
           Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
            Re: User concurrency thresholding: where do I look?  (Tom Lane, )
             Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
              Re: User concurrency thresholding: where do I look?  (Tom Lane, )
               Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                 Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                 Re: User concurrency thresholding: where do I look?  (David Boreham, )
                  Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                 Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                  Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                   Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                    Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                     Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                      Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                       Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                      Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                       Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                        Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                        Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                         Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                          Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                           Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                            Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                             Re: User concurrency thresholding: where do I look?  (Tom Lane, )
                              Re: User concurrency thresholding: where do I look?  (Robert Lor, )
                             Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                              Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                               Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                                Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                                 Re: User concurrency thresholding: where do I look?  (Alvaro Herrera, )
                                  Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                                 Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
                                  Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                                  Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                                   Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                                    Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                                  Re: User concurrency thresholding: where do I look?  (Josh Berkus, )
                                   Re: User concurrency thresholding: where do I look?  ("Jignesh K. Shah", )
                              CLOG Patch  ("Jignesh K. Shah", )
                               Re: CLOG Patch  ("Simon Riggs", )
                                Re: CLOG Patch  ("Jignesh K. Shah", )
                                 Re: CLOG Patch  ("Simon Riggs", )
                           Re: User concurrency thresholding: where do I look?  ("Simon Riggs", )
       Re: User concurrency thresholding: where do I look?  (Greg Smith, )
        Re: User concurrency thresholding: where do I look?  (Josh Berkus, )
     Re: User concurrency thresholding: where do I look?  ("Joshua D. Drake", )
    Re: User concurrency thresholding: where do I look?  (Gregory Stark, )
 Re: User concurrency thresholding: where do I look?  (Greg Smith, )

Josh Berkus <> writes:
> Alvaro,
>> Have you messed with max_connections and/or max_locks_per_transaction
>> while testing this?  The lock table is sized to max_locks_per_xact times
>> max_connections, and shared memory hash tables get slower when they are
>> full.  Of course, the saturation point would depend on the avg number of
>> locks acquired per user, which would explain why you are seeing a lower
>> number for some users and higher for others (simpler/more complex
>> queries).

> That's an interesting thought.  Let me check lock counts and see if this is
> possibly the case.

AFAIK you'd get hard failures, not slowdowns, if you ran out of lock
space entirely; and the fact that you can continue the curve upwards
says that you're not on the edge of running out.  However I agree that
it's worth experimenting with those two parameters to see if the curve
moves around at all.

Another resource that might be interesting is the number of open files.

Also, have you tried watching vmstat or local equivalent to confirm that
the machine's not starting to swap?

            regards, tom lane


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