John M McIntosh wrote:
> I'm not sure I understand your question. The change created three  
> instance variables, one being the time a switch started,
> another the time it ended, the last the total incremental milliseconds.  
> At process switch time I'd read the millisecond clock
> and do a subtraction, a validity check, then add to the total.

I don't see a problem in the instance variable changes in Process.

I would like to know, if the overhead for these measurements is so low,
that there is no problem to use these modified VM and image *regularly*
(e.g. in V4). Another variant would be to compile a special VM and to
generate a special image for these measurements (with or without V4). In
between would be a VM flag controlling if the time should be updated or
not, which could be set by a prim.

My estimation is, that the time hit is low compared with the time for
the computations outside the time measurements above. But this highly
depends from the time needed to read the millisecond clock, so I'm not
sure here; at this point there also could be a difference between
different platforms. Moreover in Squeak process changes are rare, since
a Squeak process only will be preempted by a higher prioritized one (no
preemptive multitasking between processes with the same priority) or by
intention (I have seen it in e.g. 'tally' profiling measures).


I hope my intent and questions are more clear now.


Greetings
Stephan

> 
> On Oct 8, 2004, at 1:03 PM, Stephan Rudlof wrote:
> 
> 
>>John and others,
>>
>>John M McIntosh wrote:
>>
>>>A long time ago I did a change set that added dispatch clock time to  
>>>an
>>>instance variable in
>>>Process when the VM process scheduler switched processes.
>>
>>John: Do you remember how much the overhead regarding VM speed has  
>>been?
> 
> 
> --
> ======================================================================== 
> ===
> John M. McIntosh <johnmci at smalltalkconsulting.com> 1-800-477-2659
> Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
> ======================================================================== 
> ===
> 
> 
> 

-- 
Stephan Rudlof (sr at evolgo.de)
   "Genius doesn't work on an assembly line basis.
    You can't simply say, 'Today I will be brilliant.'"
    -- Kirk, "The Ultimate Computer", stardate 4731.3