Re: postgresql-8.0.1 performance tuning

От: Mark Kirkwood
Тема: Re: postgresql-8.0.1 performance tuning
Дата: ,
Msg-id: 429D6242.6000804@paradise.net.nz
(см: обсуждение, исходный текст)
Ответ на: Re: postgresql-8.0.1 performance tuning  (Cosimo Streppone)
Список: pgsql-performance

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postgresql-8.0.1 performance tuning  ("Martin Fandel", )
 Re: postgresql-8.0.1 performance tuning  (John A Meinel, )
  Re: postgresql-8.0.1 performance tuning  ("Martin Fandel", )
 Re: postgresql-8.0.1 performance tuning  (Cosimo Streppone, )
  Re: postgresql-8.0.1 performance tuning  (Mark Kirkwood, )
   Re: postgresql-8.0.1 performance tuning  (Cosimo Streppone, )
    Re: postgresql-8.0.1 performance tuning  (Mark Kirkwood, )
   SHMMAX / SHMALL Was (Re: postgresql-8.0.1 performance tuning)  (Paul McGarry, )
    Re: SHMMAX / SHMALL Was (Re: postgresql-8.0.1 performance  (Mark Kirkwood, )
     Re: SHMMAX / SHMALL Was (Re: postgresql-8.0.1 performance tuning)  ("Martin Fandel", )
      Re: SHMMAX / SHMALL Was (Re: postgresql-8.0.1 performance  (Mark Kirkwood, )
       Re: SHMMAX / SHMALL Was (Re: postgresql-8.0.1 performance tuning)  ("Martin Fandel", )
  Re: postgresql-8.0.1 performance tuning  ("Steinar H. Gunderson", )
   Re: postgresql-8.0.1 performance tuning  (Cosimo Streppone, )
   Re: postgresql-8.0.1 performance tuning  ("Martin Fandel", )
   Re: postgresql-8.0.1 performance tuning  ("Martin Fandel", )
    Re: postgresql-8.0.1 performance tuning  ("Martin Fandel", )
     Re: postgresql-8.0.1 performance tuning  ("Martin Fandel", )

Cosimo Streppone wrote:
> Mark Kirkwood ha scritto:
>
>> Cosimo Streppone wrote:
>>
>>> ######### Config ############
>>>
>>>> /etc/sysctl.conf:
>>>> kernel.shmall = 786432000
>>>> kernel.shmmax = 786432000
>>>
>>>
>>> I think you have a problem here.
>>> kernel.shmmax should *not* be set to an amount of RAM, but
>
>
> Sorry, I thought "shmall" but written "shmmax".
> Thanks Mark!
>

Hehe - happens to me all the time!

On the shmall front - altho there is *probably* no real performance
impact setting it to the same as shmmax (i.e. allowing 4096 allocations
of size shmmax!), it is overkill. In addition it does allow for a DOS by
a program that allocates thousands of segments (or somehow starts
thousands of Pg servers on different ports...)!

For a dedicated Pg server I would size shmall using a calculation along
the lines of:

shmall = (no. of postgresql servers) * (shmmax/4096)


If there are other daemons on the box that need to use shared memory,
then add their likely requirements to shmall too!

cheers

Mark


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