Messages in this thread | | | From | Andi Kleen <> | Subject | Re: Why Semaphore Hardware-Dependent? | Date | Tue, 29 Aug 2006 12:56:54 +0200 |
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On Tuesday 29 August 2006 12:05, David Howells wrote:
>Because i386 (and x86_64) can do better by using XADDL/XADDQ.
x86-64 has always used the spinlock based version.
> On i386, CMPXCHG also ties you to what registers you may use for what to some > extent.
We've completely given up these kinds of micro optimization for spinlocks, which are 1000x as critical as rwsems. And nobody was able to benchmark a difference.
It is very very likely nobody could benchmark a difference on rwsems either.
While I'm sure it's an interesting intellectual exercise to do these advanced rwsems it would be better for everybody else to go for a single maintainable C implementation.
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