Re: [PATCH] local_irq_disable removal

[Ingo Molnar]

* Zwane Mwaikambo <zwane@xxxxxxxxxxx> wrote:

> > Interesting .. So "cli" takes 7 cycles , "sti" takes 7 cycles. The current 
> > method does "lea" which takes 1 cycle, and "or" which takes 1 cycle. I'm 
> > not sure if there is any function call overhead .. So the soft replacment 
> > of cli/sti is 70% faster on a per instruction level .. So it's at least 
> > not any slower .. Does everyone agree on that?
> 
> Well you also have to take into account the memory access, so it's not 
> always that straightforward.

preempt_count resides in the first cacheline of 'current thread info' 
and is almost always cached. It's the same cacheline that 'current', 
'smp_processor_id()' are using.

	Ingo
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