[croquet] Linux: My computer is so fast ...

David P. Reed dpreed at reed.com
Tue Jan 23 21:19:19 UTC 2007


The Linux SqueakVM may run strangely under parallels - Linux has a 
complex way of using the various Intel hardware clocks, and the 
Parallels IntelVM emulates the hardware clocks.   In particular the TSC 
(high res) clock runs at a rate dependent on the cpu frequency, which 
changes dynamically under OS X, but that dynamic change cannot easily be 
detected in a virtualized Intel machine.   Wondering why you don't use 
the OS X vm?

Ken Causey wrote:
> Perhaps a time correction through an NTP daeomon or the like?
>
> Ken
>
> P.S. Of course that only makes sense if the clock used is the actual
> time and not something like a clock time independent value like
> milliseconds since program start.  Maybe.  I'm not sure how that is
> calculated either, truth be told.
>
> On Tue, 2007-01-23 at 20:43 +0100, Bert Freudenberg wrote:
>   
>> ... that it finishes before it even started.
>>
>> I just ran Croquet's tests on a MacBook Pro with Ubuntu Linux in the  
>> Parallels PC emulator:
>>
>> 	CroquetVMTests new quickLatencyTest
>>
>> results in
>>
>> 	#(2.451390797266446e6 1073741822 0.023 3)
>>
>> which is a test failure. The first value is supposed to be the  
>> average number of milliseconds for a local network roundtrip, the  
>> second the maximum. Strange values. Looking at the actual test runs,  
>> here are the results sorted by occurrence, values in hex:
>>
>>   a SortedCollection(63481->'16r0' 4374->'16r1' 131->'16r2' 61- 
>>  >'16r3FFFFFFE' 45->'16r3FFFFFFD' 44->'16r3' 29->'16r4' 20- 
>>  >'16r3FFFFFFC' 10->'16r7' 3->'16r6' 3->'16r5' 2->'16r8' 1- 
>>  >'16r3FFFFFFB')
>>
>> The method to measure the runtime is [...] timeToRun. How could that  
>> possibly answer a negative amount?! Only if the millisecond clock  
>> turns backwards. The new Apple machines indeed are very fast, but  
>> *that* fast?
>>
>> - Bert -
>>
>>
>>
>>
>>     



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