[cpp-threads] Proposing a layered Thread API

[Kevlin Henney]

Lawrence Crowl <lawrence.crowl at gmail.com> writes
>On 9/3/06, Kevlin Henney <kevlin at curbralan.com> wrote:
>> I also don't see why a reference count plus a copy will be expensive.
>> There is no significant space overhead to a reference count and no
>> additional allocations required and, unless someone is pathologically
>> making copies all over the place, there is little cost associated with
>> copying. Perhaps you could clarify where the reference count plus copy
>> overhead is.
>
>The expense is in the atomic increment and decrement operations.  In
>particular, non-atomic operations are just a few cycles acting on the
>cache closest to the processor.  The atomic operations need to coordinate
>with other processors, and this can run to a hundred cycles.

If there are no copies there is no cost associated with copying. If 
there is some copying there is some cost. If there is pathological 
copying there is a great cost. What I was trying to determine was where 
the implied significant, extra costs were as I'm struggling to see them.

Kevlin
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