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Tasks and garbage collection
3 posts by 2 authors  



James Fairbanks 	

12/8/15


Task objects, which are created by @task f(args), hold on to some resources. How do those resources get released? 

For example, if I have a function that makes a task that doesn't return, what happens?

function doforever()
     while true
          produce(true)
     end
end

function g(n::Int)
     t = @task doforever()
     for i in 1:n
           return consume(t)
     end
end

for i in 1:10000
    g(5)
end

How many tasks are still in existence at the end of this loop?
Do the resources associated with a task get released as soon as all references to the Task instance go out of scope?
Does the task need to be "done" before releasing the resources?

I expect the answers to be 1 (the main task), yes (at first available gc cycle), no.
The docs page http://docs.julialang.org/en/release-0.4/stdlib/parallel/ doesn't really cover these issues so I am not sure.
Also is there a reference that details what resources Task instances possess? 
 


James Fairbanks 	

12/8/15


I noticed a typo in my original post function g should have been:

function g(n::Int)
     t = @task doforever()
     for i in 1:n
           println(consume(t))
     end
end
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Seth 	

12/8/15


I just did an experiment with:

function doforever()
   while true
       produce(zeros(100000,10000)) # ~8 gigabytes
   end
end

and the memory deallocated when I did an explicit gc().
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