limitiation on memory allocation
cswiger at mac.com
Mon Mar 12 18:48:59 UTC 2007
On Mar 12, 2007, at 11:20 AM, Dima Sorkin wrote:
> 2) 'maxdsiz' - Yes, as long as I keep 'maxdsiz + maxssiz' below
> memory size - everything is fine. Single process allocates
> up to 'maxdsiz'.
> When tried to put 'maxdsiz' > phys mem size,
> indeed the system failed to boot, in all modes:
> multiuser, singleuser, safe.
> So I derive from here that there is no way to cause a _single process_
> on FreeBSD to allocate more than physical memory size (?)
It is certainly possible to configure FreeBSD to allow a single
process to access more memory than is phyiscally installed. For
example, I have a machine with 512MB of RAM, and set:
...in /boot/loader.conf, and this works just fine. Admittedly, when
a process does exceed 512MB in dsize, the system starts swapping
quite a bit, but that's how virtual memory works.
However, you cannot set maxdsiz greater than 4GB  if you are
running a 32-bit version of FreeBSD. Enabling PAE will let the
kernel access more than 4GB of physical RAM, but nothing is going to
let a 32-bit system give more than 4 GB  to a single process...if
you want to do that, then you'll need to switch to running a 64-bit
version of FreeBSD.
: Well, 3.5GB or 3GB, actually...due to the top portion of address
space being occupied by PCI device space and the kernel.
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