[Fwd: Re: Memory Problem]

-------- Message transféré --------

> De: Flavio Henrique Araque Gurgel <flavio(at)4linux(dot)com(dot)br>
> À: pgsql-admin <pgsql-admin(at)postgresql(dot)org>
> Cc: Nicolas Michel <nicolas(dot)michel(at)lemail(dot)be>
> Sujet: Re: Memory Problem
> Date: Sat, 4 Apr 2009 10:58:45 -0300 (BRT)
>
>
> Hello!
>
> > Thank you very much. I didn't know that. I set my shmmax to 4000000000 but you're right, we will see to use a 64 bits system ;)
>
> My experience with this amount of memory in Debian Etch works much better in a 64bit environment. BIGMEM kernel handles pages in a way that the performance is a bit degraded.

Thank you for this piece of information.

>
> > I wanted to give to postgres 4GB. So I tryied to set shmmax to 4Go :
> >
> > sysctl kernel.shmmax=4294967296
> >
> >
> > But it doesn't work : if I launch after this modification this command :
> >
> > sysctl kernel.shmmax
> >
> > it gives me this response :
> >
> > kernel.shmmax = 0
> >
> > Why? Is there a limit to shmmax?
>
> I don't see limits in shmmax but the command you're typing is wrong.
> To set a value you need to do:
> sysctl -w kernel.shmmax=VALUE

I read the man of sysctl and it seems that you're right. But I always
set my sysctl variables without the -w switch and it seems that it used
to work.

>
> or alternatively:
> cat VALUE > /proc/sys/kernel/shmmax
>
> Don't forget to write in your /etc/sysctl.conf:
> kernel.shmmax=VALUE
> Without spaces. This will make your setting persistent.
>
> Regards
> Flavio