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From: peirce@claris.com (Michael Peirce)
Newsgroups: comp.lang.ada
Subject: Re: Two questions
Message-ID: <9274@claris.com>
Date: 29 Mar 89 18:35:57 GMT
References: <674@uva.UUCP>
Reply-To: peirce@claris.com (Michael Peirce)
Organization: Claris Corporation, Mountain View CA
List-Id: <comp.lang.ada>

>2. When a task has completed its execution, termination is delayed until all
>   dependent tasks have terminated (9.4.6).  As a result, our program
>   fills up all memory with completed tasks unable to terminate.  Why is
>   this?  Can something be done about it (without altering task dependency)?
>
>
>We have the impression that Ada was designed to deal with a small
>number of large tasks, whereas we are trying to create a large number
>of small tasks.  Is this true?  Does it matter?
>

The way we dealt with this problem was to reuse our tasks.  We had
a situation where we wanted to dispatch a handler task for each incoming
request from the network. In Vax Ada, the tasks weren't removed from
memory until after the program exited the scope of the task declaration.
This meant that in our outter most scope, a terminated tasks' memory
was never reclaimed.  To solve this problem, we set up a task manager that 
kept a list of idle tasks and whenever a task was requested it would reuse 
one of these tasks first before creating a new one.  Of course, each task
ended up having some extra code at the beginning to handle initialization
and some at the end to handle returning itself to the free list.  This
overhead was minimal though.

With this type of scheme in place we were able to run our system for 
days or weeks at a time using "new" tasks for each message, but never
running into memory usage problems.  

-- michael