memory limitations per process

[Ivan Voras]

af300wsm at gmail.com wrote:
> Hi,
> 
> I'm running into a per process memory limit at work (on Windoze though),
> but I'm wondering what's the limit per process in FreeBSD for 32 bit
> systems, ie i386? Is it 4gb or 2? From stuff I found on the Net, I'm
> guessing 4gb, but wanted to ask anyway. It seems to be an implementation
> deal limiting the windows world to 2gb per process rather than hardware
> limitations.

Your question is vague.

A 32-bit process can only access 4 GB of memory, but all processes also
have a bit of memory "reserved" for the kernel. On FreeBSD the
accessible memory for processes is closer to 3 GB than 2 or 4. See this
discussion for details: http://wiki.freebsd.org/KVA_PAGES

Also, FreeBSD processes have administrative limits to their size set by
defaults. See for example this:
http://unix.derkeiler.com/Mailing-Lists/FreeBSD/questions/2008-11/msg01363.html
. If you want to use the whole 3 GB for a process, you'll have to
increase maxdsiz. Note that you may need to experiment with this size
since your BIOS will probably not let you use 4 GB of physical memory
for the OS except if you enable PAE, and it's possible to create an
unbootable system by messing with kernel memory limits. You should
probably experiment on the loader command line first, not in the
loader.conf file.

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