kern/47434: loading dtrace fails with ENOMEM in a vanilla amd64 kernel

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

>Number:         47434
>Category:       kern
>Synopsis:       loading dtrace fails with ENOMEM in a vanilla amd64 kernel
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jan 11 21:00:00 +0000 2013
>Originator:     Taylor R Campbell <campbell+netbsd%mumble.net@localhost>
>Release:        NetBSD 6.99.15
>Organization:
>Environment:
System: NetBSD ... 6.99.15 NetBSD 6.99.15 (RIAKERN) #0: Wed Nov 28 01:20:09 UTC 
2012 
root@...:/home/riastradh/netbsd/current/obj.amd64/sys/arch/amd64/compile/RIAKERN
 amd64
Architecture: amd64
Machine: amd64
>Description:

        Loading the dtrace modules (solaris.kmod, dtrace.kmod,
        fbt.kmod, sdt.kmod) into a vanilla amd64 kernel fails with
        ENOMEM.  To get them to load I had to bump NKL2_KIMG_ENTRIES in
        sys/arch/amd64/include/pmap.h from 16 to 32.

>How-To-Repeat:

        Try to load dtrace into a vanilla amd64 kernel.

>Fix:

        Bump NKL2_KIMG_ENTRIES from 16 to 32 to work around it.
        Solving the problem so that we don't have to reserve large
        chunks of kva in advance for modules would be trickier and
        require some nontrivial compiler and linker work to cross
        branch distance barriers, but would be nice.