[Swift-devel] Coaster capabilities for release 0.9

[Ioan Raicu]

Mihael Hategan wrote:
> On Tue, 2009-04-21 at 21:31 -0500, Ioan Raicu wrote:
>   
>>     
>> I did this with timers. Each task has a max wall time, that dictates
>> when the timer will fire for a particular task to mark its completion.
>> I simulated up to 1M processors, and billions of tasks, so the timer
>> based approach in Java seems to scale quite well to extremes of
>> millions of concurrent timers.
>>     
>
> One problem is that if you use the same timer object, the events they
> generate aren't really concurrent (which is why it's so scalable). Each
> timer is a thread that goes through a loop of sorted tasks. I think a
> pool of a few timers would do the trick though.
>
>   
Right, I know. I implemented it with a pool of threads.
>>  If you are interested, I can dig through the Falkon code where I
>> implemented this logic of emulating workers.
>>     
>
> Right. That's almost all that's needed, but there's also the current
> time which needs to be faked given that planning depends on how much
> time is left in a block, and that depends on what time it is now.
>   
In my case, there were two ways to remove timer events. One way was to 
let them fire themselves when the time asked elapsed. This is one timer 
per task. The other reason to remove a timer event would be that the 
worker's allocation ended. This is done also with timers, one per 
worker. Overall, I used real time as a reference time, and the 
implementation could keep up with 1000s, maybe even 10000s of timer 
events per second.

Ioan
> Seems fairly straightforward.
>
>
>
>   

-- 
===================================================
Ioan Raicu, Ph.D.
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Distributed Systems Laboratory
Computer Science Department
University of Chicago
1100 E. 58th Street, Ryerson Hall
Chicago, IL 60637
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Email: iraicu at cs.uchicago.edu
Web:   http://www.cs.uchicago.edu/~iraicu
http://dev.globus.org/wiki/Incubator/Falkon
http://dsl-wiki.cs.uchicago.edu/index.php/Main_Page
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