[Simh] vax idle for NetBSD

[Mark Pizzolato]

On Tuesday, November 27, 2018 at 12:09 PM, Paul Koning wrote:
> > On Nov 15, 2018, at 9:32 AM, Paul Koning wrote:
> >
> > I just installed NetBSD/VAX V8 on SIMH.  The documentation mentions "set
> cpu idle=netbsd", but it doesn't work -- I'm stuck at 100% CPU.
> >
> > I'm running it on the microvax3900 simulator, if that makes a difference.  Any
> > ideas?
> 
> Update: it's working now.  I had some configuration issues before with
> networking etc. but I don't see how that explains idle failure.  I know
> sometimes, in some simulators, it takes a while to get to idle, but I thought I
> had waited long enough.
> 
> In any case, this appears to be a false alarm and it does work correctly.

Well, when I followed the directions you pointed out, I did see what you 
had reported.  A little deeper observation strongly suggested that the
OS execution flow that happens on NetBSD/VAX during idling had changed 
from how things were working when I had worked through how to get things 
well behaved idling under simh.  

I haven't yet had the time to look closely at the OS code to determine 
what exactly was happening.  If you're seeing things OK now, maybe, there 
is some sort of garbage collection activity going on, which runs for a while 
and then somehow eventually stabilizes to the known idle execution 
pattern.

NetBSD is the fundamental exception for operating systems running under 
simh due to the fact that it is still an actively developed and evolving 
operating system.  As a result, the idle detection pattern will always have
to evolve along with the evolving OS.

- Mark