Re: Proposal of tunable fix for scalability of 8.4

From: Tom Lane
Subject: Re: Proposal of tunable fix for scalability of 8.4
Date: ,
Msg-id: 29836.1236826066@sss.pgh.pa.us
(view: Whole thread, Raw)
In response to: Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey)
Responses: Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah")
Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey)
List: pgsql-performance

Tree view

Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
 Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
  Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
   Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
  Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
   Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
    Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
     Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
     Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
      Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
       Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
        Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
        Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
         Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
          Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
  Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
   Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
    Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
     Re: Proposal of tunable fix for scalability of 8.4  (decibel, )
      Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
       Re: Proposal of tunable fix for scalability of 8.4  (Josh Berkus, )
    Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
     Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
      Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
      Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
       Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
        Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
         Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
          Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
         Re: Proposal of tunable fix for scalability of 8.4  (decibel, )
        Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
        Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
         Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
          Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
           Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
         Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
         Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
          Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
           Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
            Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
          Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
           Re: Proposal of tunable fix for scalability of 8.4  (decibel, )
            Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
             Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
              Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
      Re: Proposal of tunable fix for scalability of 8.4  (Greg Smith, )
   Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
    Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
    Re: Proposal of tunable fix for scalability of 8.4  (Greg Smith, )
     Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
      Re: Proposal of tunable fix for scalability of 8.4  (Robert Haas, )
       Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
        Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
        Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
         Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
         Re: Proposal of tunable fix for scalability of 8.4  (, )
          Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
           Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
            Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
        Re: Proposal of tunable fix for scalability of 8.4  (Heikki Linnakangas, )
         Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
          Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
          Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
         Re: Proposal of tunable fix for scalability of 8.4  (Matthew Wakeling, )
          Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
           Re: Proposal of tunable fix for scalability of 8.4  (Matthew Wakeling, )
            Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
             Re: Proposal of tunable fix for scalability of 8.4  (Matthew Wakeling, )
             Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
              Re: Proposal of tunable fix for scalability of 8.4  (Matthew Wakeling, )
               Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
           Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
            Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
           Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
            Re: Proposal of tunable fix for scalability of 8.4  (Matthew Wakeling, )
             Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
             Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
             Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
          Re: Proposal of tunable fix for scalability of 8.4  (Heikki Linnakangas, )
           Re: Proposal of tunable fix for scalability of 8.4  (Matthew Wakeling, )
       Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
        Re: Proposal of tunable fix for scalability of 8.4  (Robert Haas, )
         Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
          Re: Proposal of tunable fix for scalability of 8.4  (Robert Haas, )
           Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
            Re: Proposal of tunable fix for scalability of 8.4  (Robert Haas, )
             Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
              Re: Proposal of tunable fix for scalability of 8.4  (Alvaro Herrera, )
               Re: Proposal of tunable fix for scalability of 8.4  (Alvaro Herrera, )
                Re: Proposal of tunable fix for scalability of 8.4  (Alvaro Herrera, )
                 Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
                  Re: Proposal of tunable fix for scalability of 8.4  (Robert Haas, )
                   Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
           Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
         Re: Proposal of tunable fix for scalability of 8.4  (Bruce Momjian, )
          Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
           Re: Proposal of tunable fix for scalability of 8.4  (Bruce Momjian, )
         Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
      Re: Proposal of tunable fix for scalability of 8.4  (Greg Smith, )
     8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
      Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
      Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
       Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Alan Stange, )
        Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
         Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
          Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
           Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Robert Haas, )
            Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
            Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
           Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Bruce Momjian, )
            Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Bruce Momjian, )
      Re: 8.4 Performance improvements: was Re: Proposal of tunable fix for scalability of 8.4  (Greg Smith, )
   Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
    Re: Proposal of tunable fix for scalability of 8.4  (Grzegorz Jaśkiewicz, )
     Re: Proposal of tunable fix for scalability of 8.4  ("Kevin Grittner", )
      Re: Proposal of tunable fix for scalability of 8.4  (Ron, )
     Re: Proposal of tunable fix for scalability of 8.4  (Gregory Stark, )
      Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
    Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
     Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
      Re: Proposal of tunable fix for scalability of 8.4  (Alvaro Herrera, )
       Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
        Re: Proposal of tunable fix for scalability of 8.4  (decibel, )
      Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
    Re: Proposal of tunable fix for scalability of 8.4  (Tom Lane, )
     Re: Proposal of tunable fix for scalability of 8.4  (Scott Carey, )
    Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )
 Re: Proposal of tunable fix for scalability of 8.4  (Simon Riggs, )
  Re: Proposal of tunable fix for scalability of 8.4  ("Jignesh K. Shah", )

Scott Carey <> writes:
> If there is enough lock contention and a common lock case is a short lived shared lock, it makes perfect sense sense.
Fewer readers are blocked waiting on writers at any given time.  Readers can 'cut' in line ahead of writers within a
certainscope (only up to the number waiting at the time a shared lock is at the head of the queue).  Essentially this
clumpsup shared and exclusive locks into larger streaks, and allows for higher shared lock throughput. 
> Exclusive locks may be delayed, but will NOT be starved, since on the next iteration, a streak of exclusive locks
willoccur first in the list and they will all process before any more shared locks can go. 

That's a lot of sunny assertions without any shred of evidence behind
them...

The current LWLock behavior was arrived at over multiple iterations and
is not lightly to be toyed with IMHO.  Especially not on the basis of
one benchmark that does not reflect mainstream environments.

Note that I'm not saying "no".  I'm saying that I want a lot more
evidence *before* we go to the trouble of making this configurable
and asking users to test it.

            regards, tom lane


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