I've also seen this behavior on Win2k and WinNT.  It's only in more
recent VMs.  Squeak 2.5 did not exhibit this behavior.

- Stephen

> -----Original Message-----
> From: squeak-dev-admin at lists.squeakfoundation.org 
> [mailto:squeak-dev-admin at lists.squeakfoundation.org] On 
> Behalf Of Mike Rutenberg
> Sent: Thursday, January 24, 2002 1:00 PM
> To: Squeak-dev at lists.squeakfoundation.org
> Cc: Andreas.Raab at gmx.de; Mike Rutenberg
> Subject: Weird Windows 2000 scheduling behaviour with Squeak VM
> 
> 
> If I do a long Squeak calculation like
> 	[true] whileTrue: [12 / 4]
> the Windows 2000 scheduler will only occasionally give any 
> other "normal priority" Win32 process any CPU time.  Other 
> processes, even those who are "on top", will be almost 
> entirely deprived of cycles.  For example, the TaskManager 
> CPU graph or list of running processes no longer updates 
> regularly, often pausing for 20 seconds.  Similarly 
> InternetExplorer and the FileManager become very unresponsive.
> 
> I have also noticed the same behavior if I compact a Celeste 
> mail database (which involves lots of memory allocations and 
> IO) rather than an endless simple loop.
> 
> Interestingly, a second simultaneously running Squeak VM is 
> not affected while the first runs the endless loop.  It 
> responds normally though all of this, and does not seem 
> noticeably slowed down, for instance quickly opening a change sorter.
> 
> When I am able to finally bring up the TaskManager, I can 
> eventually lower the priority of Squeak.exe and the system 
> immediately becomes responsive again.
> 
> As a test, I wrote a small C program to duplicate this endless loop. 
> When I run it, the CPU meter pegs at 100%, but the system 
> does not become unresponsive.
> 
> Has anyone else seen anything like this under Windows NT or 2000?  Is
> this a side effect of something done intentionally in the VM? 
>   I do not
> remember seeing problem under Windows 98.
> 
> Mike
>