pmap vs. large Zorro III space

[Radosław Kujawa <radoslaw.kujawa%c0ff33.net@localhost>]

Hello list,

Yesterday I've installed Matay Prometheus PCI, which allocates very large Zorro 
III space (512MB). 

As soon as kernel was loaded, panic occured with  "uvm_km_suballoc: unable to 
allocate space in parent map" error. Looks like the problem is during 
pmap_init. I think this is the same problem we've seen on the list in december. 
I was able to reproduce this on a recent GENERIC kernel (from 
releng.netbsd.org). 

See this blurry pic for the full trace: http://c0ff33.net/pmappanic1.jpg

I checked out pmap_init and I see only two places where uvm_km_suballoc is 
called. One is allocation of segment table map, and the other is allocation of 
page tables map. Michael Hitch suggested, that it is probaby related to page 
tables map allocation and that I might want to increase VM_KERNEL_PT_PAGES 
(defined in vmparam.h). I've tried increasing it a bit (to 12, 15, 24), but no 
change was visible. Increasing the value too much (for example to 32) leads to 
a different kind of panic: http://c0ff33.net/pmappanic2.jpg

I won't act like I know what's going on in pmap code, because I don't know. Any 
sugestions would be highly appreciated.

--
Best regards,
Radosław Kujawa