Re: Ada GC (Hans Boehm)
4 Feb 1996 00:58:49 -0500

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From: (Hans Boehm)
Newsgroups: comp.compilers,comp.lang.ada
Date: 4 Feb 1996 00:58:49 -0500
Organization: Xerox Palo Alto Research Center
References: 96-01-037 96-01-146 96-02-003
Keywords: Ada, GC, realtime (Robert Dewar) writes:

>Well there are several applicable algorithms, but we don't need to get
>into that to argue this point. Just consider an application which can
>successfully use fixed-length blocks. In this case it is trivial to
>write a dynamuc storage allocator with constant time allocation and
>deallocation, and no fragmentation effects. Note that fixed sized
>blocks do not significantly help GC, but they certainly help
>allocators with explicit deallocation.

>I have seen a number of real time systems written in this kind of
>allocation environment.

>By having separate pools for separate lengths of blocks, one can
>extend this technique to multiple sizes of blocks.

Certainly. But that doesn't make a very good general purpose
allocator. Thus the application would presumably include its own
allocator. That's equally possible in a garbage collected system or
one with explicit deallocation. Thus it seems to me the issue is moot
for this kind of application. Even a non-real-time GC is fine if you
don't use it to allocate while the system is running.

(I would claim fixed size blocks also help a GC, but I think that's
beside the point here. And the improvement is probably less
substantial, depending on the GC.)

Hans-J. Boehm

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