Re: Pre-allocation of shared memory ... - Mailing list pgsql-hackers

From Andrew Dunstan
Subject Re: Pre-allocation of shared memory ...
Date
Msg-id 32859.199.90.235.43.1055435327.squirrel@www.dunslane.net
Whole thread Raw
In response to Re: Pre-allocation of shared memory ...  (Bruce Momjian <pgman@candle.pha.pa.us>)
Responses Re: Pre-allocation of shared memory ...  (Bruce Momjian <pgman@candle.pha.pa.us>)
List pgsql-hackers
A couple of points:

. It is probably a good idea to put do this via /etc/sysctl.conf, which will
be called earlyish by init scripts (on RH9 it is in the network startup
file, for some reason).

. The setting is not available on all kernel versions AFAIK. The admin needs
to check the docs. I have no idea when this went into the kernel, and no
time to spend finding out. Even if we knew, it might have gone into vendor
kernels at other odd times  - there are often times when the vendors are in
advance of the officially released kernels.

Andrew


Bruce wrote:
>
> OK, new text is:
>
>       <para>
>        Linux has poor default memory overcommit behavior.  Rather than
>        failing if it can not reserve enough memory, it returns success,
>        but later fails when the memory can't be mapped and terminates
>        the application with <literal>kill -9</>.  To prevent
>        unpredictable process termination, use:
> <programlisting>
> sysctl -w vm.overcommit_memory=3
> </programlisting>
>        Note, you will need enough swap space to cover all your memory
>        needs.
>       </para>
>      </listitem>
>     </varlistentry>
>
> ---------------------------------------------------------------------------
>
> Tom Lane wrote:
>> Bruce Momjian <pgman@candle.pha.pa.us> writes:
>> > OK, doc patch attached and applied.  Improvements?
>>
>> I think it would be worth spending another sentence to tell people
>> exactly what the symptom looks like, ie, backends dying with signal 9.
>>
>>             regards, tom lane
>>
>
> --
>  Bruce Momjian                        |  http://candle.pha.pa.us
>  pgman@candle.pha.pa.us               |  (610) 359-1001
>  +  If your life is a hard drive,     |  13 Roberts Road
>  +  Christ can be your backup.        |  Newtown Square, Pennsylvania
>  19073
>
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