Reality check? compat.ia32.maxdsiz in jailed "32-bit" environment

Tom Evans at
Mon Nov 4 16:23:37 UTC 2013

On Mon, Nov 4, 2013 at 3:49 PM, David Wolfskill <david at> wrote:
> I am supporting a performance-sensitive software development
> environment that:
>> I have (also) started experimenting with increasing compat.ia32.maxdsiz
> beyond its default of 512MB: Initially, I kicked it to 2GB; more
> recently, I tried setting it to 3GB.
> While I have not noticed any negative issues from either of the above
> non-default settings, I have done but limited testing with concurrent
> software builds in my test environment.

IIRC, when running on pure i386, setting kern.maxdsiz limits the
amount of kernel address space (or rather, dsize+KVA = 4 GB), and so
you had to be careful when increasing kern.maxdsiz.

This probably has no effect on a i386 on amd64 jail though.



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