CentOS - Dec 2013 - Why the huge shmmax default setting?

Fresh load of Centos6/64 from new ISO (downloaded 2 weeks ago?) and 
getting set up with PostgreSQL, one of the typical steps is to increase 
shmmax from its normal, conservative value (eg: 32 MB or something) to 
something far more aggressive.

But in recent installs of CentOS 6, this value is generally huge, 
typically larger than the RAM installed on the machine! For example, 
fresh installs on systems with 32 GB of RAM, this is already set to 
68719476736 (64 GB)

This large value doesn't really make sense to me - can somebody explain 
why the change to such a large value?

-Ben

On 12/17/2013 4:33 PM, Lists wrote:
> This large value doesn't really make sense to me - can somebody explain
> why the change to such a large value?
its just a limit, it has no impact unless someone claims too much shared 
memory.

the only place it makes sense to set it small is on a shared ssytem with 
potentially hostile users who might think its funny to allocate too much 
and cause a denial of service.... eg, Students.



-- 
john r pierce                                      37N 122W
somewhere on the middle of the left coast