Re: Question about memory allocations

From: Tom Lane
Subject: Re: Question about memory allocations
Date: ,
Msg-id: 4918.1176568674@sss.pgh.pa.us
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In response to: Re: Question about memory allocations  (Ron)
List: pgsql-performance

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how to efficiently update tuple in many-to-many relationship?  (Drew Wilson, )
 Re: how to efficiently update tuple in many-to-many relationship?  ("Merlin Moncure", )
 Re: how to efficiently update tuple in many-to-many relationship?  (Tom Lane, )
  Re: how to efficiently update tuple in many-to-many relationship?  (Drew Wilson, )
   Re: how to efficiently update tuple in many-to-many relationship?  (Tom Lane, )
    Re: how to efficiently update tuple in many-to-many relationship?  (Drew Wilson, )
     Re: how to efficiently update tuple in many-to-many relationship?  (Tom Lane, )
      Re: how to efficiently update tuple in many-to-many relationship?  (Drew Wilson, )
       Re: how to efficiently update tuple in many-to-many relationship?  (Tom Lane, )
        Question about memory allocations  (Steve, )
         Re: Question about memory allocations  (Tom Lane, )
          Re: Question about memory allocations  (Steve, )
         Re: Question about memory allocations  (Greg Smith, )
          Re: Question about memory allocations  (Steve, )
         Re: Question about memory allocations  (Andrew McMillan, )
          Re: Question about memory allocations  (Steve, )
           Re: Question about memory allocations  (Ron, )
            Re: Question about memory allocations  (Tom Lane, )
           Re: Question about memory allocations  (Carlos Moreno, )
            Re: Question about memory allocations  ("Jan de Visser", )

Ron <> writes:
> One of the reasons for the wide variance in suggested values for pg
> memory use is that pg 7.x and pg 8.x are =very= different beasts.
> If you break the advice into pg 7.x and pg 8.x categories, you find
> that there is far less variation in the suggestions.
> Bottom line: pg 7.x could not take advantage of larger sums of memory
> anywhere near as well as pg 8.x can.

Actually I think it was 8.1 that really broke the barrier in terms of
scalability of shared_buffers.  Pre-8.1, the buffer manager just didn't
scale well enough to make it useful to use more than a few hundred meg.
(In fact, we never even bothered to fix the shared-memory-sizing
calculations to be able to deal with >2GB shared memory until 8.1;
if you try it in 8.0 it'll probably just crash.)

            regards, tom lane


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