Messages in this thread | | | Date | Tue, 30 Nov 1999 17:18:30 +0100 (CET) | From | Andrea Arcangeli <> | Subject | Re: AVL trees vs. Red-Black trees |
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On Tue, 30 Nov 1999, Oliver Xymoron wrote:
>know what the lowest common denominator was. What is the weakest ordering >model the kernel will support?
About stability: the weakest ordering supported right now is the Alpha where both reads and writes can be reordered.
About performance: the most finegriend barriers we have exported to common code are the most finegriend for the Alpha but according to the spin_unlock thread on l-k, the IA32 SMP system could implement a barrier that only avoids things to be moved from up to down but that would allow further speculative reads to be moved before the barrier. Such kind of barrier could be implemented by doing a dummy write on the next free stack slot. I don't think it would make sense to export to common code such an half barrier and I believe it worth to only use it for implementing the spin_unlock internally as we are just doing since 2.3.30pre3.
So basically the current common denominator seems just fine to me.
Andrea
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