[erlang-questions] Cost of hibernation

[Valentin Micic]

Thanks Pablo,

Just want to confirm that when you say:

"The time the processes where hibernated was in the range of seconds…"

you mean that an average time between two messages addressing the same process can be measured in seconds?

Kind reagards

V/


On 22 Jul 2013, at 5:26 PM, Pablo Polvorin wrote:

> Hello,
> On 22 July 2013 11:57, Valentin Micic <v@REDACTED> wrote:
>> Dear all,
>> 
>> Erlang reference manual makes a following statement regarding
>> erlang:hibernate/3
>> 
>> "erlang:hibernate(Module, Function, Args)
>> 
>> Types:
>> 
>> Module = Function = atom()
>> Args = [term()]
>> 
>> Puts the calling process into a wait state where its memory allocation has
>> been reduced as much as possible, which is useful if the process does not
>> expect to receive any messages in the near future.
>> 
>> …"
>> 
>> I have never used the hibernate function fearing that performance penalty to
>> be paid may be to high.  In other words, I never really had to use it ;-)
>> 
>> But now that I do, may I kindly ask if there is anyone out there that did
>> successfully used this feature and has a clear idea regarding performance
>> penalty.
>> Would it be cheaper to store and retrieve a context using ETS (which would
>> certainly complicate programming), or would a call to hibernate do the
>> trick?
>> 
>> Maybe another way to ask this question could be: what is the cost of calling
>> a garbage collection frequently?
>> 
>> Also, would anyone care to define a meaning of "the near future" within this
>> context? Should one measure "the near future"  in milliseconds, seconds or
>> minutes?
> As vague as it is, maybe this helps:
> I had used it in a few systems.  In tsung for example (with hundreds
> of thousands of processes simulating user behavior),  there was a big
> memory saving,  and the time the processes where hibernated was in the
> range of seconds,  not minutes.    The difference in cpu usage in that
> case was barely noticeable
> 
>> 
>> Kind regards
>> 
>> V/
>> 
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> 
> 
> 
> -- 
> Pablo Polvorin
> ProcessOne
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