Subj : Re: A question about atomic_ptr
To   : comp.programming.threads
From : Joe Seigh
Date : Tue Apr 12 2005 02:18 pm

On Mon, 11 Apr 2005 19:25:02 -0700, Chris Thomasson <_no_damn_spam_cristom@_no_damn_comcast.net_spam> wrote:

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>> There seems to be some attraction in c.l.c++.m to smart pointers that
>> have almost no overhead, the deferred reference counting being
>> promoted by Andrei but there's no such thing a a free lunch.  Deferred
>> reference counting does Boehm style GC against the thread stacks and
>> that requires a "stop the world while we GC" which has huge performance
>> implications in multi-threading.
>
> Actually, you mentioned a scheme that would allow for "deferred reference
> counting" using per-thread lock-free single-producer/consumer queues.
> Pushing a node ( reference adjustment request ) into a "local" per-thread
> queue is certainly less overhead than performing an interlocked-operation on
> a "shared" variable. I don't think you would need to use DWCAS either. The
> logic could be isolated in the "collection phase"...
>
> There is just one problem, if the collection cycles could not keep up with
> user allocs/frees the applications memory usage could climb out of control.
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>
The deferred reference counting mentioned by Andrei seems to be a different
scheme.  I think there's a way to solve most of the problems here.  I'll
just add it to my list of things I don't have time to do.  Actually, I
have time, just not time to do pointless things.  I mean, just how
many more GC schemes do *I* need?

-- 
Joe Seigh

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