On Mon, Jul 12, 1999 at 07:09:58PM -0700, Mike Smith wrote:
> > Although function calls are more expensive than inline code,
> > they aren't necessarily a lot more so, and function calls to
> > non-locked RMW operations are certainly much cheaper than
> > inline locked RMW operations.
>
> This is a fairly key statement in context, and an opinion here would
> count for a lot; are function calls likely to become more or less
> expensive in time?
Others have answered this question, but I thought I'd point out
that there is another alternative that is likely to be faster
than indirect function calls on some architectures: inline
branched code. So you still have a global variable selecting
locked/non-locked, but it's a boolean, rather than a pointer.
Your atomic macros are then { if (atomic_lock) asm("lock;foo");
else asm ("foo"); }
You might be interested in the paper:
"Efficient Dynamic Dispatch without Virtual Function Tables. The
SmallEiffel Compiler." Olivier ZENDRA, Dominique COLNET, Suzanne
COLLIN. 12th Annual ACM SIGPLAN Conference on Object-Oriented
Programming, Systems, Languages, and Applications (OOPSLA'97),
Volume 32, Issue 10 - Atlanta, GA, USA, October 1997, pages 125-141.
http://SmallEiffel.loria.fr/papers/papers.html#OOPSLA97
as a justification for that approach.
--
Andrew
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