port-m68k/54254: Switch 68K to 8KB pages to increase available address space

[cmhanson%eschatologist.net@localhost]

>Number:         54254
>Category:       port-m68k
>Synopsis:       Switch 68K to 8KB pages to increase available address space
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-m68k-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 31 20:40:00 +0000 2019
>Originator:     Chris Hanson
>Release:        netbsd-8
>Organization:
>Environment:
>Description:
In trying to build python27 from pkgsrc-2018Q3, my HP 9000/433s with 128MB of RAM and 384MB of swap running netbsd-8 panicked due to address space exhaustion.

I discussed this on the port-hp300 list and Izumi Tsutsui said that there are restrictions in the 68K pmap code that are causing this, and a simple workaround is to increase the page size to 8KB by setting PGSHIFT to 13.

I set PGSHIFT to 13 and rebuilt the kernel and it works to build python27 and everything else I've tried, so I think this should be adopted until such time as the pmap code can be revised to cover larger address spaces.
>How-To-Repeat:
Try to build python27 from pkgsrc-2018Q3 on hp300 running netbsd-8 with sufficient virtual memory; you will exhaust address space before the build completes.
>Fix:
Increase page size to 8KB by setting PGSHIFT to 13.