Re: hot restart of posgtresql - Mailing list pgsql-admin

From Tom Lane
Subject Re: hot restart of posgtresql
Date
Msg-id 17445.1183517505@sss.pgh.pa.us
Whole thread Raw
In response to Re: hot restart of posgtresql  (Alvaro Herrera <alvherre@commandprompt.com>)
List pgsql-admin
Alvaro Herrera <alvherre@commandprompt.com> writes:
> Tom Lane wrote:
>> ngaleyev@wavelengthmail.com writes:
>>> heres my sysctl:
>>> kernel.shmmax=4294967296
>>> kernel.shmall=536870912
>>
>> Why have you got SHMALL set to half a GB when you have Postgres
>> configured to ask for over 3 GB?

> Hmm, isn't shmall measured in pages?

Depends on platform, which he didn't say ... but if it is a platform
that measures in pages, I wonder whether that value is provoking an
integer overflow somewhere.  I don't think Linux allows more than
about 2 million, for instance.

> I think the problem may be that he changed the settings in sysctl.conf
> but he hasn't rebooted since, so the kernel is running with other
> settings.  Trying with sysctl -w to change the actual values might prove
> helpful.

But his DB *was* running before, so somehow the active sysctl settings
are different now than they were.  I was betting on there having been
a manual tweak to sysctl that never got made in the configuration file,
and thus got lost on reboot.

            regards, tom lane

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