Re: [PATCH] local_irq_disable removal

[Daniel Walker]

On Sat, 11 Jun 2005, Ingo Molnar wrote:

> 
> * Esben Nielsen <simlo@xxxxxxxxxx> wrote:
> 
> > > the jury is still out on the accuracy of those numbers. The test had 
> > > RT_DEADLOCK_DETECT (and other -RT debugging features) turned on, which 
> > > mostly work with interrupts disabled. The other question is how were 
> > > interrupt response times measured.
> > > 
> > You would accept a patch where I made this stuff optional?
> 
> I'm not sure why. The soft-flag based local_irq_disable() should in fact 
> be a tiny bit faster than the cli based approach, on a fair number of 
> CPUs. But it should definitely not be slower in any measurable way.


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?

Daniel

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