conf/94509: Setting PMAP_SHPGPERPROC in kernel config has no effect

[Thomas Hurst]

>Number:         94509
>Category:       conf
>Synopsis:       Setting PMAP_SHPGPERPROC in kernel config has no effect
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Mar 15 18:20:07 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Thomas Hurst
>Release:        FreeBSD 6.1-PRERELEASE amd64
>Organization:
Newzbin Limited
>Environment:
System: FreeBSD search1.newzbin.com 6.1-PRERELEASE FreeBSD 6.1-PRERELEASE #0: Wed Mar 15 16:25:27 UTC 2006     root at search1.newzbin.com:/usr/obj/usr/src/sys/X4100_SEARCHSERVER  amd64

>Description:
	This machine has a process group which shares ~2GB of anonymous memory between
	a bunch of processes, resulting in:
	
	"collecting pv entries -- suggest increasing PMAP_SHPGPERPROC"

	Setting "options PMAP_SHPGPERPROC=400" in amd64 kernel config has no effect,
	meaning I had to edit amd64/pmap.c directly to increase the available PV entries.
>How-To-Repeat:
	Check upper limit on sysctl vm.zone | grep PV
	Set PMAP_SHPGPERPROC in kernel config to a value != 200.
	Recompile/install kernel.  Recheck limit, find it hasn't changed.

	Verified on 2 different amd64 systems, both running very recent
	RELENG_6.
>Fix:

	Workaround is to edit the constant in /sys/amd64/amd64/pmap.c directly


>Release-Note:
>Audit-Trail:
>Unformatted: