[Vm-dev] microsecond timing for GC work

Andreas Raab andreas.raab at gmx.de
Wed Jan 20 01:44:26 UTC 2010

David T. Lewis wrote:
> On Tue, Jan 19, 2010 at 04:28:47PM -0800, Andreas Raab wrote:
>>> Would anyone object to the addition of a primitive that answers
>>> Posix seconds (to some reasonable precision) plus time zone offset?
>>> This would be a named primitive in addition to John's microsecond
>>> primitive.
>> I'm not sure what the point of it would be. Both of you are speaking in 
>> riddles at this point; it would be good if you could spell out the 
>> issues more clearly.
> The clock in Squeak is done in local time (UTC translated to local
> seconds in the VM before it is reported to the image). Consider a
> Squeak image running in a locale with daylight savings time. Once
> per year in the fall, there is a period of one hour during which the
> Squeak clock has "jumped backwards" one hour. All of the values of the
> Squeak clock are repeated during for the next hour. The values are
> ambiguous, and the calculation of durations and times based on them
> is problematic.

Ah, I see. Thanks for clearing this up. How does that relate to posix 
seconds as stated above? Are posix seconds UTC? If not, shouldn't we 
rather make sure all time in UTC (regardless of epoch) and leave it to 
the image to work out the timezone it's in? That seems the better 
long-term option to me.

   - Andreas

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