[Vm-dev] microsecond timing for GC work

[David T. Lewis]

On Sun, Jan 17, 2010 at 03:57:10PM -0800, John M McIntosh wrote:
>  
> The attached change set and sq.h enable microsecond timing for GC work. 
> Please review for consideration for VMMaker. 
> 
> I've added a named primitive
> 
> primitiveMicrosecondClock
> 	"This is a named (not numbered) primitive in the null module (ie the VM)"
> 	self export: true.
> 	self pop: 1 thenPush: (self positive64BitIntegerFor: (self ioMicroSeconds)).
> 
> 
> I used the 'sqLong' data type, but we don't seem to have a usqLong type to get unsigned long long  ? 
> Since in this case I'd like the 64bit value to be positive only value... 
> 

I would not worry too much about using a sqLong here. If you report time
in microseconds since the Posix epoch, you can go nearly 300 centuries
before overflowing a 64 bit signed integer.

  bigLong := (2 raisedTo: 63) - 1.
  biggestMicrosecAsSeconds := bigLong / 1000000.
  secondsPerYear := 365.25 * 24 * 60 * 60.
  maxYears := biggestMicrosecAsSeconds / secondsPerYear.
  lastYear := 1970 + maxYears asInteger ==> 294241

Dave