>Number:         35577
>Category:       kern
>Synopsis:       unionfs and nullfs spending too much I/O time
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 08 17:35:00 +0000 2007
>Originator:     Juan RP
>Release:        NetBSD 4.99.9
>Organization:
The NetBSD Project
>Environment:
System: NetBSD nocturno 4.99.9 NetBSD 4.99.9 (Nocturno) #17: Wed Feb 7 17:59:28 CET 2007 juan@nocturno:/home/juan/build/obj/sys/arch/i386/compile/Nocturno i386
Architecture: i386
Machine: i386
>Description:

	With last vnode locking changes made by chs@, working
	with a stackable filesystem (I tried nullfs and unionfs) 
	spends a reasonable amount of time in I/O
	(hard disk is continuosly reading something).

	I was trying to test the newlock2 branch, so I downloaded
	it into ~/src-newlock2, I mounted it with nullfs like:

	$ mount_null ~/src-newlock2/sys /usr/src/sys
	
	and ran build.sh to build a new kernel, the depend process
	took >5 minutes! when 2 weeks ago it took <1m, same
	for unionfs.

>How-To-Repeat:
	Just try to use a null or union mount and see how slow 
	is.
>Fix:
	Yes, please.