Re: Performance under contention

От: Tom Lane
Тема: Re: Performance under contention
Дата: ,
Msg-id: 21911.1291845739@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Performance under contention  (Robert Haas)
Ответы: Re: Performance under contention  (Robert Haas)
Список: pgsql-performance

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Performance under contention  (Ivan Voras, )
 Re: Performance under contention  ("Kevin Grittner", )
  Re: Performance under contention  (Ivan Voras, )
   Re: Performance under contention  (Jignesh Shah, )
    Re: Performance under contention  (Omar Kilani, )
   Re: Performance under contention  ("Kevin Grittner", )
    Re: Performance under contention  (Ivan Voras, )
     Re: Performance under contention  (Craig Ringer, )
      Re: Performance under contention  (Ivan Voras, )
      Re: Performance under contention  (Vitalii Tymchyshyn, )
       Re: Performance under contention  ("Kevin Grittner", )
 Re: Performance under contention  ("Kevin Grittner", )
  Re: Performance under contention  (Ivan Voras, )
 Re: Performance under contention  (Greg Smith, )
  Re: Performance under contention  (Ivan Voras, )
 Re: Performance under contention  (Robert Haas, )
  Re: Performance under contention  (Robert Haas, )
  Re: Performance under contention  (Jignesh Shah, )
   Re: Performance under contention  (Jignesh Shah, )
   Re: Performance under contention  (Robert Haas, )
    Re: Performance under contention  (Tom Lane, )
     Re: Performance under contention  (Dave Crooke, )
     Re: Performance under contention  (Robert Haas, )
    Re: Performance under contention  (Ivan Voras, )
     Re: Performance under contention  (Robert Haas, )
      Re: Performance under contention  (Ivan Voras, )
      Re: Performance under contention  (Віталій Тимчишин, )
       Re: Performance under contention  (Ivan Voras, )
       Re: Performance under contention  (Robert Haas, )
        Re: Performance under contention  (Robert Haas, )
         Re: Performance under contention  (Tom Lane, )
          Re: Performance under contention  (Robert Haas, )
           Re: Performance under contention  (Tom Lane, )
            Re: Performance under contention  (Robert Haas, )

Robert Haas <> writes:
> 2010/12/8 Tom Lane <>:
>> Now, it's possible that you could avoid *ever* needing to search for a
>> specific PROCLOCK, in which case eliminating the hash calculation
>> overhead might be worth it.

> That seems like it might be feasible.  The backend that holds the lock
> ought to be able to find out whether there's a PROCLOCK by looking at
> the LOCALLOCK table, and the LOCALLOCK has a pointer to the PROCLOCK.

Hm, that is a real good point.  Those shared memory data structures
predate the invention of the local lock tables, and I don't think we
looked real hard at whether we should rethink the fundamental
representation in shared memory given the additional local state.
The issue though is whether any other processes ever need to look
at a proc's PROCLOCKs.  I think at least deadlock detection does.

            regards, tom lane


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