[boost] [shared_ptr] Why aren't atomic integer operations used?

From: Don G (dongryphon_at_[hidden])
Date: 2005-01-02 21:24:38

I was reading the shared_ptr and shared_count classes and noticed
that a mutex is used when it appears that atomic inc/dec could be
used instead. Unless I am missing something? The atomic operations
would be far better in terms of resource usage. It seems (to me
anyway) far too expensive to have a mutex allocated for every object
under management.

On platforms where atomic inc/dec don't exist (if there are any<g>),
a pool of mutexes be used. The object's pointer would be hashed to
produce the appropriate mutex, thereby ensuring a consistent mutex
for each object and a low likelihood of undesired contention. Also,
an upper bound on the number of mutexes allocated vs. objects.

Best,
Don

PS: This is now only my 2nd post, so if I am not following proper
protocol, please feel free to advise.

                
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