Re: Big trouble with memory !!

Hervé Piedvache wrote:
> Hi,
> 
> We have switched to kernel 2.6.11.6 from kernel 2.4.26 ... since this date we 
> have many troubles with PostgreSQL and most of them seems to be memory 
> troubles.
> 
> As far as we can see, kernel kills the postmaster process when it begins to 
> use swap. You can see the output from dmesg at the bottom of the message. 
> The first thing I am not sure to understand is that the kernel should kill 
> processes to reallocate memory only when physical memory and swap memory are 
> exhausted, shouldn't it ?
> Second thing: it seems to be related to our kernel switch as it did not happen 
> before that.
> 
> This can occur when queries / a vacuum require too much memory to run.
> I have configured my kernel with these options:
> # shared mem 
> kernel.shmmax= 641604096
> # semaphore
> kernel.sem = 250 32000 100 400
> fs.file-max=65536
> # overcommit
> vm.overcommit_memory=2
> 
> Does anyone can explain me why I have this problem and how to resolve it ?
> 
> This server is a dedicated PostgreSQL server with 4Gb of RAM.

You might want to try vm.overcommit_memory=1. You don't appear to be the 
only one suffering from an over-zealous oom-killer.

http://www.ussg.iu.edu/hypermail/linux/kernel/0501.2/1295.html
http://www.linuxquestions.org/questions/history/291119

--
   Richard Huxton
   Archonet Ltd