#	$NetBSD: LAST_MINUTE,v 1.2.4.3 2006/10/16 20:28:41 ghen Exp $

This file contains important information on the NetBSD 3.0 release that
did not make it into the main documentation.

[i386]

	Machines configured with more than 2 GB of physical memory may
	experience hangs due to running out of kernel virtual space,
	which is needed for kernel datastructures such as file system
	metadata buffers.  Various kernel subsystems (including the
	file system metadata cache) automatically adjust their memory
	usage based on the amount of physical memory in the system,
	but this method over-allocates the available kernel virtual
	space (1 GB) when the amount of physical memory greatly
	exceeds the amount of kernel virtual space.

	The only reliable workaround currently known for this problem
	is to increase the amount of virtual space available to the
	kernel by adding these lines to the kernel config file:

	options KERNBASE_LOCORE="0x80000000"
	makeoptions TEXTADDR="0x80100000"

	Be sure you "make clean" in your kernel build directory after
	adding these lines!

	This will increase the kernel virtual space to 2 GB, but this
	has the drawback that the application virtual space is
	decreased from 3 GB to 2 GB (since the 32-bit address space
	supported by the hardware must be shared between the kernel
	and application on this architecture).

	If any application that is to run on the system needs more
	than 2 GB of application virtual space, then this work-around
	cannot be used.  A possible alternative work-around is to
	reduce the amount of physical memory used for file system
	buffers by using sysctl to change the value of the tunable
	"vm.bufmem_hiwater" to a lower value, perhaps 200000000
	(200 MB).

[all platforms]

	The NetBSD implementation of the POSIX thread library
	(libpthread) has an option (enabled by setting the environment
	variable "PTHREAD_CONCURRENCY" to a number greater than 1)
	which tells the library to run threads of a single process on
	more than one CPU simultaneously.  This feature has various
	known problems and will often result in the pthread library
	aborting due to internal assertion failures, and sometimes
	it will even result in the entire systems crashing.  Use of
	this feature is not recommended for anyone other than those
	working to fix the problems with it.