MINIROOTSIZE is unreproducible limited

[Markus Mueller <openbsduser_(_at_)_priv_(_dot_)_de>]

Hi OpenBSD Users,

I retraced the limit of MINIROOTSIZE in Kernel 3.7(stable). It is not 
(no longer) 32768 (16 MB), as Chris Kuethe wrote on 2003-01-31 6:06:29 
at tech_(_at_)_openbsd, but exactly 17473 (8736,5 KBs). Ok, maybe this value is 
only with my config file for Kernel 3.7(stable). You can find Chris 
Kuethes message under 
http://marc.theaimsgroup.com/?l=openbsd-tech&m=104399330809455&w=2

I tested and neared me to this value 17473:

13000    Works!
16000    Works!
17000    Works!
17250    Works!
17375    Works!
17438    Works!
17469    Works!
17477    Works!
17481    Works!
17483    Works!
17474    isadma0 at isapanic: isadmaattach: can not create DMA map (same 
as in 17500.gif)
17485    isadma0 at isapanic: isadmaattach: can not create DMA map (same 
as in 17500.gif)
17500    isadma0 at isapanic: isadmaattach: can not create DMA map (see 
17500.gif)
17657    isadma0 at isapanic: isadmaattach: can not create DMA map (same 
as in 17500.gif)
18000    kernel: page fault trap, code=0 (see 18000.gif)
23000    Immediate Reboot
32000    Immediate Reboot

I am worrying... is 17483 realy a safe value for MINIROOTSIZE? How can I 
make sure that I have a low enough number, so that I won't get one or 
more problems, at booting and espacialy also on runtime?

Anybody may give me a hint about the cause why this special value is the 
limit? How to increase this? Why is a too big number a problem, and why 
is it unhandled? Because it is implemented on compiling/linking level?

I didn't insert the image (rdsetroot), I just compiled the kernel with 
this values for MINIROOTSIZE. But it is also crashing if I insert the image.

The config and the gifs you can find under

 http://priv.de/minirootsize.16.07.05/

Please include me in CC in your answer(s), cause I am (currently) not on 
your mailinglists.

Regards,
Markus Mueller