[Vm-dev] Sista/Scorch callbacks v. clock jitter

Clément Bera bera.clement at gmail.com
Sun Oct 29 14:49:43 UTC 2017

On Sat, Oct 28, 2017 at 5:55 PM, Ben Coman <btc at openinworld.com> wrote:

> hi Clement,
> I was watching your nice talk on Pharo Optimizing JIT Internals. At 14:40
> [1]
> you mention VM call-back to Scorch DNU-style.  I was just curious how that
> might affect the jitter of the DelayScheduler waiting for the
> timingSemaphore set by "primSignal: timingSemaphore atMilliseconds:
> millisecondNextTick"
> to be signalled by the VM?

I am not sure I understand the question. Only 1 optimisation call-back is
running at once (It disables itself when started, re-enables itself at the
end). If another green thread takes over the runtime, the optimisation of
the function will time out. The other green thread can then be optimized.
Does this answer the question ?

> [1] https://youtu.be/yDKaHphbFow?list=PLJ5nSnWzQXi_
> THfKwhzxFwbXy00YTi0uv&t=883
> cheers -ben
> P.S. Later when you say Sista will be an optional VM - curious whether
> Sista might be switched on/off from within the VM? or just a command line
> flag? or an actual different VM (which adds complexity to system
> management).
> Different VMs. In the Sista VM you can turn things on/off. In the default
VM you only have unoptimized behavior. Once the image has Sista methods it
requires the Sista VM unless you switch it off and revert all optimised

Clément Béra
Pharo consortium engineer
Bâtiment B 40, avenue Halley 59650 Villeneuve d'Ascq
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