kmem_map auto-sizing and size dependencies

[Artem Belevich]

On Mon, Jan 21, 2013 at 1:06 PM, Pawel Jakub Dawidek <pjd at freebsd.org> wrote:
> On Fri, Jan 18, 2013 at 08:26:04AM -0800, mdf at FreeBSD.org wrote:
>> >  Should it be set to a larger initial value based on min(physical,KVM) space
>> >  available?
>>
>> It needs to be smaller than the physical space, [...]
>
> Or larger, as the address space can get fragmented and you might not be
> able to allocate memory even if you have physical pages available.

+1 for relaxing upper limit.

I routinely patch all my systems that use ZFS to allow kmem_map size
to be larger than physical memory. Otherwise on a system where most of
RAM goes towards ZFS ARC I used to eventually run into dreaded
kmem_map too small panic.

--Artem