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: 13654.1280263202@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas)
Ответы: Re: Pooling in Core WAS: Need help in performance tuning.  (Robert Haas)
Re: Pooling in Core WAS: Need help in performance tuning.  (Craig Ringer)
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 Thu, Jul 22, 2010 at 5:29 PM, Andres Freund <> wrote:
>>> The problem is harder for us because a backend can't switch identities
>>> once it's been assigned to a database. �I haven't heard an adequate
>>> explanation of why that couldn't be changed, though.

>> Possibly it might decrease the performance significantly enough by
>> reducing the cache locality (syscache, prepared plans)?

> Those things are backend-local.  The worst case scenario is you've got
> to flush them all when you reinitialize, in which case you still save
> the overhead of creating a new process.

"Flushing them all" is not zero-cost; it's not too hard to believe that
it could actually be slower than forking a clean new backend.

What's much worse, it's not zero-bug.  We've got little bitty caches
all over the backend, including (no doubt) some caching behavior in
third-party code that wouldn't get the word about whatever API you
invented to deal with this.

            regards, tom lane


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