mmap max size (qemu VM memsize limit)

Gergely CZUCZY phoemix at
Wed Nov 21 06:50:57 PST 2007


I'm trying to set up a qemu with 4G memory to the host system
on a 7-BETA2, and I've hit some kind of limit in freebsd.

When i give more then ~2000MB of memory to qemu, it returns
an after trying to mmap() it, saying "Could not map physical memory".

At the end of mmap(2) there's a note saying:
"     The len argument is limited to the maximum file size or available user-
     land address space.  Files may not be able to be made more than 1TB large
     on 32 bit systems due to file systems restrictions and bugs, but address
     space is far more restrictive.  Larger files may be possible on 64 bit

I guess I've found this limit. I've tried to check a few sysctls but I wasn't
able to find the one effecting this limit.

Could someone point me into the right direction in increasing the maximum
mmap-able size?


Gergely Czuczy
mailto: gergely.czuczy at

Weenies test. Geniuses solve problems that arise.
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