Re: Pooling in Core WAS: Need help in performance tuning.

От: Tom Lane
Тема: Re: Pooling in Core WAS: Need help in performance tuning.
Дата: ,
Msg-id: 3774.1280293774@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas)
Список: pgsql-performance

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Need help in performance tuning.  (Harpreet singh Wadhwa, )
 Re: Need help in performance tuning.  ("Kevin Grittner", )
 Re: Need help in performance tuning.  (Craig Ringer, )
  Re: Need help in performance tuning.  (Samuel Gendler, )
   Re: Need help in performance tuning.  (Tom Lane, )
    Re: Need help in performance tuning.  (Craig Ringer, )
     Re: Need help in performance tuning.  (Harpreet singh Wadhwa, )
     Re: Need help in performance tuning.  (Craig Ringer, )
     Re: Need help in performance tuning.  (Harpreet singh Wadhwa, )
      Re: Need help in performance tuning.  ("Jorge Montero", )
     Re: Need help in performance tuning.  (Bruce Momjian, )
    Re: Need help in performance tuning.  (Brad Nicholson, )
     Re: Need help in performance tuning.  ("Kevin Grittner", )
      Re: Need help in performance tuning.  (Matthew Wakeling, )
       Re: Need help in performance tuning.  ("Kevin Grittner", )
        Re: Need help in performance tuning.  (Matthew Wakeling, )
         Re: Need help in performance tuning.  ("Kevin Grittner", )
          Re: Need help in performance tuning.  ("Jorge Montero", )
           Re: Need help in performance tuning.  ("Kevin Grittner", )
         Re: Need help in performance tuning.  (Greg Smith, )
          Re: Need help in performance tuning.  ("Kevin Grittner", )
           Re: Pooling in Core WAS: Need help in performance tuning.  (Josh Berkus, )
            Re: Pooling in Core WAS: Need help in performance tuning.  (Craig Ringer, )
             Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
              Re: Pooling in Core WAS: Need help in performance tuning.  (Josh Berkus, )
               Re: Pooling in Core WAS: Need help in performance tuning.  (Tom Lane, )
                Re: Pooling in Core WAS: Need help in performance tuning.  (Matthew Wakeling, )
                 Re: Pooling in Core WAS: Need help in performance tuning.  (Craig Ringer, )
                  Re: Pooling in Core WAS: Need help in performance tuning.  ("Kevin Grittner", )
                   Re: Pooling in Core WAS: Need help in performance tuning.  (Rajesh Kumar Mallah, )
                    Re: Pooling in Core WAS: Need help in performance tuning.  (Rajesh Kumar Mallah, )
                    Re: Pooling in Core WAS: Need help in performance tuning.  (Greg Smith, )
                     Re: Pooling in Core WAS: Need help in performance tuning.  (Rajesh Kumar Mallah, )
                     Re: Pooling in Core WAS: Need help in performance tuning.  (Rajesh Kumar Mallah, )
                      Re: Pooling in Core WAS: Need help in performance tuning.  (Rajesh Kumar Mallah, )
                       Re: Pooling in Core WAS: Need help in performance tuning.  (Tatsuo Ishii, )
                        Re: Pooling in Core WAS: Need help in performance tuning.  (Rajesh Kumar Mallah, )
                         Re: Pooling in Core WAS: Need help in performance tuning.  (Tatsuo Ishii, )
                    Re: Pooling in Core WAS: Need help in performance tuning.  (Hannu Krosing, )
                  Re: Pooling in Core WAS: Need help in performance tuning.  (Hannu Krosing, )
                  Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                   Re: Pooling in Core WAS: Need help in performance tuning.  (Andres Freund, )
                    Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                     Re: Pooling in Core WAS: Need help in performance tuning.  (Tom Lane, )
                      Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                       Re: Pooling in Core WAS: Need help in performance tuning.  (Tom Lane, )
                        Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                         Re: Pooling in Core WAS: Need help in performance tuning.  (Tom Lane, )
                        Re: Pooling in Core WAS: Need help in performance tuning.  (Vitalii Tymchyshyn, )
                        Re: Pooling in Core WAS: Need help in performance tuning.  (Josh Berkus, )
                         Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                          Re: Pooling in Core WAS: Need help in performance tuning.  (Tom Lane, )
                           Re: Pooling in Core WAS: Need help in performance tuning.  (Andres Freund, )
                           Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                            Re: Pooling in Core WAS: Need help in performance tuning.  (Josh Berkus, )
                      Re: Pooling in Core WAS: Need help in performance tuning.  (Craig Ringer, )
                  Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                   Re: Pooling in Core WAS: Need help in performance tuning.  ("Joshua D. Drake", )
                    Re: Pooling in Core WAS: Need help in performance tuning.  (Hannu Krosing, )
                     Re: Pooling in Core WAS: Need help in performance tuning.  ("Joshua D. Drake", )
                      Re: Pooling in Core WAS: Need help in performance tuning.  (Hannu Krosing, )
                     Re: Pooling in Core WAS: Need help in performance tuning.  ("Joshua D. Drake", )
                   Re: Pooling in Core WAS: Need help in performance tuning.  (Hannu Krosing, )
                    Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                     Re: Pooling in Core WAS: Need help in performance tuning.  (Hannu Krosing, )
                      Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                       Re: Pooling in Core WAS: Need help in performance tuning.  (Andres Freund, )
                       Re: Pooling in Core WAS: Need help in performance tuning.  (Craig Ringer, )
                        Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas, )
                   Re: Pooling in Core WAS: Need help in performance tuning.  (Scott Carey, )
                    Re: Pooling in Core WAS: Need help in performance tuning.  (Joshua Tolley, )
                     Re: Pooling in Core WAS: Need help in performance tuning.  (Greg Smith, )
                      Re: Pooling in Core WAS: Need help in performance tuning.  (Andres Freund, )
                      Re: Pooling in Core WAS: Need help in performance tuning.  (Craig Ringer, )
                       Re: Pooling in Core WAS: Need help in performance tuning.  (Dimitri Fontaine, )
                       Re: Pooling in Core WAS: Need help in performance tuning.  (Hannu Krosing, )
                   Re: Pooling in Core WAS: Need help in performance tuning.  ("Joshua D. Drake", )
                Re: Pooling in Core WAS: Need help in performance tuning.  (Dimitri Fontaine, )
                 Re: Pooling in Core WAS: Need help in performance tuning.  (Magnus Hagander, )
             Re: Pooling in Core WAS: Need help in performance tuning.  (Scott Carey, )
            Re: Pooling in Core WAS: Need help in performance tuning.  (Samuel Gendler, )
          Re: Need help in performance tuning.  (Jesper Krogh, )
           Re: Need help in performance tuning.  (Greg Smith, )
            Re: Need help in performance tuning.  ("Pierre C", )
     Re: Need help in performance tuning.  (Mark Kirkwood, )
    Re: Need help in performance tuning.  (Robert Haas, )
    Re: Need help in performance tuning.  (Hannu Krosing, )
     Re: Need help in performance tuning.  (Scott Marlowe, )
      Re: Need help in performance tuning.  ("Kevin Grittner", )
       Re: Need help in performance tuning.  (Hannu Krosing, )
 Re: Pooling in Core WAS: Need help in performance tuning.  (Rajesh Kumar Mallah, )

Robert Haas <> writes:
> On Tue, Jul 27, 2010 at 9:56 PM, Tom Lane <> wrote:
>> Other than the fork() cost itself and whatever authentication activity
>> there might be, practically all the startup cost of a new backend can be
>> seen as cache-populating activities. �You'd have to redo all of that,
>> *plus* pay the costs of getting rid of the previous cache entries.
>> Maybe the latter costs less than a fork(), or maybe not. �fork() is
>> pretty cheap on modern Unixen.

> I agree that the gain is minimal of itself; after all, how often do
> you need to switch databases, and what's the big deal if the
> postmaster has to fork a new backend?  Where I see it as a potentially
> big win is when it comes to things like parallel query.  I can't help
> thinking that's going to be a lot less efficient if you're forever
> forking new backends.

Color me unconvinced.  To do parallel queries with pre-existing worker
processes, you'd need to hook up with a worker that was (at least) in
your own database, and then somehow feed it the query plan that it needs
to execute.  I'm thinking fork() could easily be cheaper.  But obviously
this is all speculation (... and Windows is going to be a whole 'nother
story in any case ...)

            regards, tom lane


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