Re: Setting up a database for 10000 concurrent users

On Mon, 5 Sep 2005, [UTF-8] Poul Mц╦ller Hansen wrote:

> I'm trying to setup a database for 10000 concurrent users for a test.
> I have a system with 1GB of RAM where I will use 512MB for PostgreSQL.
> It is running SuSE 9.3
>
> I have changed SHMMAX & SHMALL
> echo "536870912" >/proc/sys/kernel/shmmax
> echo "536870912" >/proc/sys/kernel/shmall
>
> and max_connections = 10000 in postgresql.conf
>
> When trying to start the database server it leaves this in the log.
> Calculated the values should be
> SEMMNI = 10000 / 16
> SEMMNS = (10000 / 16) * 17 "plus room for other applications" How much
> should that be ?
> And where can I change those values on a 2.6 kernel ?
>

The file /proc/sys/kernel/sem contains 4 numbers

SEMMSL The maximum semaphores per semaphore set.
SEMMNS A system-wide limit on the number of
semaphores in all semaphore sets.
SEMOPM The maximum number of operations that may
be specified in a semop(2) call.
SEMMNI A system-wide limit on the maximum number
of semaphore identifiers.

Look "man proc"

So just do something like
echo "250 32000 32 16000" > /proc/sys/kernel/sem
(compute the exact numbers by yourself)

But I really doubt that it it possible/reasonable to have 10000
simultaneous connections.

Also you can setup the semaphore numbers using sysctl
sysctl -w kernel.sem="250 32000 32 16000"

Regards,
Sergey

*****************************************************
Sergey E. Koposov
Max-Planck Institut fuer Astronomie
Web: http://lnfm1.sai.msu.ru/~math
E-mail: math(at)sai(dot)msu(dot)ru