Re: Tasks unleashed

[Craig Carey <research@ijs.co.nz>]

On Fri, 2 May 2003 13:21:13 +0200, Jano <nono@celes.unizar.es> wrote:

>tmoran@acm.org dice...
>> >In any case, the memory thing forces to use pools of reusable tasks,
>> >it's my main and crucial conclusion.
>> 
>>   Have you considered a protected Buffer of work to do and a fixed pool of
>> tasks which queue on an entry waiting for the Buffer to have some work to
>> do (or instructions to quit)?  Then you needn't create or destroy the
>> worker tasks.
>
>That's exactly what I'm doing :) but sometimes the "fixed" compromise 
>bugs me. ITOH, normally is better to have a upper bound for things, I 
>think.


The problem of Ada tasks leaking memory, is 100% absent if the program is
written well enough and either of the 2 compilers named here, are used (in
Windows).

Recovering the memory of a task silently fails if the task was not
 finished.

** Test 1: the memory leak is completely absent:
   for K in 1 .. 20_000 loop  -- N=20,000
      X := new A.Tt;
      N := N + 1;
      X.The_End;
      delay 1.0E-30;    --  [1]
      Free (X);         --  [2]
   end loop;

ObjectAda: 596K for both N=1,000 and N=200,000
GNAT 3.15: 760K, for both N=1,000 and N=200,000

1024 / 200,000 < 1, so no memory was being leaked for each deallocated
 task (in Windows 2000, OA 7.2.2, GNAT 3.15p).

** Test 2: Lines "[1]" and "[2]" are swapped. Now the large memory leak of
the test program is confirmed.

ObjectAda: 47.8MB, N=20,000
GNAT 3.15: 20.7MB, N=20,000,  "-largs --stack=0x40000,0x8000".


Craig Carey ; Ada 95 mailing lists htp://www.ijs.co.nz/ada_95.htm