[erlang-questions] Changing scheduler behaviour to make tests less deterministic

Chris Newcombe <>
Fri Dec 29 17:55:18 CET 2006


Understood.   Thanks for considering it.

In addition to a valuable testing tool, I suspect it could be an
interesting system-tuning parameter.  The current value of 2000
reductions per quantum was presumably chosen after experiments with a
fixed set of applications, some time ago.  (Didn't I read that it was
originally 1,000, years ago?)

So different applications, running on newer hardware and newer VMs
might benefit from a different value. (SMP might make a difference
too.)    It will be interesting to try, at least.

Chris

On 12/29/06, Rickard Green <> wrote:
> We'll consider it, but I'll give no promise. If we add it, it will most
> likely not make in into R11B-3.
>
> BR,
> Rickard Green, Erlang/OTP
>
> Chris Newcombe wrote:
> > Cool.  Would you consider adding maybe a '+Q nnnn' option to allow
> > setting CONTEXT_REDS dyamically?   (The 'Q' would be mnemonic for
> > 'quantum' as in scheduler quantum of course.)
> >
> > Many thanks,
> >
> > Chris
> >
> > On 12/27/06, Rickard Green <> wrote:
> >> As of R11B-3 there will be a "modified timing" command line argument
> >> to erl (+T). It will be possible to modify the timing more or less.
> >> It will (most likely) do the following:
> >>
> >> * spawn/spawn_link/spawn_opt will schedule out the parent process
> >>   and with "heavier modified timing" force the parent to sleep
> >>   for a while. (Among the few SMP bugs we have found in our Erlang
> >>   code, most of them have been bugs where the code depended on the
> >>   parent doing some initialization before the child began
> >>   executing.)
> >> * A fixed amount of reductions will be bumped as soon as a process
> >>   is scheduled in.
> >>
> >> BR,
> >> Rickard Green, Erlang/OTP
> >
>



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