Messages in this thread | | | From | Andi Kleen <> | Subject | Re: Why Semaphore Hardware-Dependent? | Date | Mon, 28 Aug 2006 09:23:24 +0200 |
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> > I believe the reason for not doing something like this on x86 was the > fact that we still support i386 processors, which don't have the > cmpxchg instruction.
i386 emulates cmpxchg these days (other than that most likely 99.9+% of all 386s are already long beyond their MTBF, so they shouldn't be a major concern)
> That's fair enough, but I would be opposed to > making semaphores bigger
If the code was out of lined bigger wouldn't make much difference And if it worked for spinlocks I don't see why it shouldn't for semaphores.
> and slower on PowerPC because of that.
The question is if it really makes much difference. When semaphores are congested in my experience the major overhead is in the scheduler anyways.
That would leave the fast path, but does it help that much there to have a more complicated implementation? -Andi
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