6.0 and "options PREEMPTION"

[Robert Watson]

On Thu, 27 Oct 2005, Doug Poland wrote:

> 	One of the other nice benefits to the SMPVFS work is that
> 	with our fully preemptive 6.x kernel, not holding the Giant
> 	lock over the file system code lets the file system code not
> 	only preempt lower precedence kernel threads, such as
> 	background crypto operations or file system operations, but be
> 	preempted by more timing critical code, such as sound card
> 	interrupts, network I/O, and so on.
>
> Does this mean that options PREEMPTION is assumed in 6.0?  If not, could 
> someone explain or point me to some docs that will help me understand.

In FreeBSD 6.0 and higher, options PREEMPTION appears in the default 
kernel configuration (GENERIC).

When upgrading from earlier revisions, if you keep the same config file, 
you'll need to add it manually.  With the advent of "include" support in 
newer FreeBSD versions, I find I generally have my own include file 
include GENERIC, then add nodevice/nooptions to remove things I don't 
want, and device/options to add things I do want.  The SMP kernel 
configuration is an example of this, as it includes GENERIC but adds SMP.

Robert N M Watson