Re: AIM7 40% regression with 2.6.26-rc1

[Linus Torvalds]

On Wed, 7 May 2008, Ingo Molnar wrote:
> 
> [ this patch should in fact be a bit worse, because there's two more 
>   atomics in the fastpath - the fastpath atomics of the old semaphore 
>   code. ]

Well, it doesn't have the irq stuff, which is also pretty costly. Also, it 
doesn't nest the accesses the same way (with the counts being *inside* the 
spinlock and serialized against each other), so I'm not 100% sure you'd 
get the same behaviour.

But yes, it certainly has the potential to show the same slowdown. But 
it's not a very good patch, since not showing it doesn't really prove 
much.

			Linus
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