On Sun, Nov 06, 2005 at 11:02:29AM -0800, Mark Mitchell wrote: > Are you saying that you don't expect there to ever be an architecture > that might have three or more ways of doing locking? That seems rather > optimistic to me. I think we ought to plan for needing as many versions > as we have CPUs, roughly speaking.
I think this is overkill. > If we currently use the same sequences for all i486 and higher processors, > then that's a fine idea; This is pretty much true. To keep all this in perspective, folks should remember that atomic operations are *slow*. Very very slow. Orders of magnitude slower than function calls. Seriously. Taking p4 as the extreme example, one can expect a null function call in around 10 cycles, but a locked memory operation to take 1000. Usually things aren't that bad, but I believe some poor design decisions were made for p4 here. But even on a platform without such problems you can expect a factor of 30 difference. r~
