Re: shared_buffers advice

От: Alvaro Herrera
Тема: Re: shared_buffers advice
Дата: ,
Msg-id: 20100316222058.GI3037@alvh.no-ip.org
(см: обсуждение, исходный текст)
Ответ на: Re: shared_buffers advice  (Tom Lane)
Ответы: Re: shared_buffers advice  (Tom Lane)
Список: pgsql-performance

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shared_buffers advice  (Paul McGarry, )
 Re: shared_buffers advice  (Dave Crooke, )
  Re: shared_buffers advice  (Greg Smith, )
   Re: shared_buffers advice  ("Pierre C", )
    Re: shared_buffers advice  (Nikolas Everett, )
     Re: shared_buffers advice  ("Pierre C", )
      Re: shared_buffers advice  (Greg Stark, )
      Re: shared_buffers advice  (Greg Smith, )
    Re: shared_buffers advice  (Tom Lane, )
     Re: shared_buffers advice  (Greg Stark, )
      Re: shared_buffers advice  (Greg Smith, )
      Re: shared_buffers advice  (Alvaro Herrera, )
       Re: shared_buffers advice  (Tom Lane, )
        Re: shared_buffers advice  (Alvaro Herrera, )
         Re: shared_buffers advice  (Tom Lane, )
          Re: shared_buffers advice  (Alvaro Herrera, )
           Re: shared_buffers advice  (Tom Lane, )
            Re: shared_buffers advice  (Alvaro Herrera, )
       Re: shared_buffers advice  (Greg Smith, )
        Re: shared_buffers advice  (Dimitri Fontaine, )
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  [SPAM] Re: shared_buffers advice  (Ben Chobot, )
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     Re: shared_buffers advice  (Konrad Garus, )
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       Re: shared_buffers advice  (Konrad Garus, )
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 Re: shared_buffers advice  (Merlin Moncure, )
  Re: shared_buffers advice  (Konrad Garus, )
   Re: shared_buffers advice  (Merlin Moncure, )
    Re: shared_buffers advice  (Greg Smith, )
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  Re: shared_buffers advice  (Scott Marlowe, )
   Re: shared_buffers advice  (Dave Crooke, )

Tom Lane escribió:
> Alvaro Herrera <> writes:
> > Tom Lane escribi�:
> >> Reorder to what, though?  You still have the problem that we don't know
> >> much about the physical layout on-disk.
>
> > Well, to block numbers as a first step.
>
> fsync is a file-based operation, and we know exactly zip about the
> relative positions of different files on the disk.

Doh, right, I was thinking in the sync-file-range kind of API.


> > We had a customer that had a
> > performance problem because they were inserting lots of data to TOAST
> > tables, causing very frequent extensions.  I kept wondering whether an
> > allocation policy that allocated several new blocks at a time could be
> > useful (but I didn't try it).  This would also alleviate fragmentation,
> > thus helping the physical layout be more similar to logical block
> > numbers.
>
> That's not going to do anything towards reducing the actual I/O volume.
> Although I suppose it might be useful if it just cuts the number of
> seeks.

Oh, they had no problems with I/O volume.  It was relation extension
lock that was heavily contended for them.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support


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