Large memory issues on 4-STABLE

[David G. Lawrence]

> David Lawrence said:
> >   Sorry, due to design issues, it isn't possible to have virtual sizes
> >larger than about 3GB on FreeBSD. This is because the kernel is mapped in
> >the upper part of the virtual address space. Of course you can use all of
> >your 4GB of RAM - just not all of it at the same time in one process.
> 
> OK, fair enough. Is this going to be any different in FreeBSD with PAE
> (Intel's scheme for 32bit stuff using > 4GB RAM)?

   No, this has nothing to do with the size of physical memory. It is a limit
on the size of a process's virtual address space.
 
> Should I try 5.1? Or isn't 4.9 going to have PAE support anyway?

   All versions of FreeBSD have this limitation.
 
> Given what David says though, why do I have a problem with MySQL getting
> thread errors with MAXDSIZ 2048 or greater?
> 
> Why does tcsh's "limit" report datasize unlimited when MAXDSIZ is over
> 2048?

   Probably a signed arithmetic problem. 2048MB is 2^31 bits, which is the
largest number that can be represented in a 32 bit signed int.

-DG

David G. Lawrence
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