Re: Why Semaphore Hardware-Dependent?
From: Andi Kleen
Date: Tue Aug 29 2006 - 06:54:22 EST
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.
-Andi
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