Re: [PATCH] local_irq_disable removal

Daniel Walker
2005-06-11T20:52:08Z

On Sat, 11 Jun 2005, Ingo Molnar wrote:

>
> * Esben Nielsen <simlo@phys.au.dk> 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