Re: Shared buffers, db transactions commited, and write IO on Solaris

От: Tom Lane
Тема: Re: Shared buffers, db transactions commited, and write IO on Solaris
Дата: ,
Msg-id: 23286.1175184996@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones)
Ответы: Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones)
Список: pgsql-performance

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Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
 Re: Shared buffers, db transactions commited, and write IO on Solaris  (Tom Lane, )
  Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
   Re: Shared buffers, db transactions commited, and write IO on Solaris  ("dimitri k", )
    Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
     Re: Shared buffers, db transactions commited, and write IO on Solaris  (Dimitri, )
      Re: Shared buffers, db transactions commited, and write IO on Solaris  (Josh Berkus, )
       Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
        Re: Shared buffers, db transactions commited, and write IO on Solaris  (Josh Berkus, )
         Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
          Re: Shared buffers, db transactions commited, and write IO on Solaris  (Josh Berkus, )
      Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
       Re: Shared buffers, db transactions commited, and write IO on Solaris  (Dimitri, )
        Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
         Re: Shared buffers, db transactions commited, and write IO on Solaris  (Dimitri, )
   Re: Shared buffers, db transactions commited, and write IO on Solaris  (Tom Lane, )
    Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
   Re: Shared buffers, db transactions commited, and write IO on Solaris  (Greg Smith, )
 Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )
  Re: Shared buffers, db transactions commited, and write IO on Solaris  ("Jim C. Nasby", )
 Re: Shared buffers, db transactions commited, and write IO on Solaris  (Dimitri, )
  Re: Shared buffers, db transactions commited, and write IO on Solaris  (Erik Jones, )

Erik Jones <> writes:
> We've recently made a couple changes to our system that have resulted
> in a drastic increase in performance as well as some very confusing
> changes to the database statistics, specifically
> pg_stat_database.xact_commit.  Here's the details:

I'm kinda boggled too.  I can see how increasing shared buffers could
result in a drastic reduction in write rate, if the working set of your
queries fits in the new space but didn't fit in the old.  I have no idea
how that leads to a drop in number of transactions committed though.
It doesn't make sense that autovac would run less frequently, because
it's driven by number of tuples changed not number of disk writes; and
that could hardly account for a 10x drop anyway.

Did you by any chance take note of exactly which processes were
generating all the I/O or the CPU load?

            regards, tom lane


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Сообщение: Re: Shared buffers, db transactions commited, and write IO on Solaris
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Сообщение: Re: Weird performance drop