Re: [PATCH] local_irq_disable removal
From: Daniel Walker (dwalker_at_mvista.com)
Date: Sat, 11 Jun 2005 13:51:47 -0700 (PDT) To: Ingo Molnar <email@example.com>
On Sat, 11 Jun 2005, Ingo Molnar wrote:
> * Esben Nielsen <firstname.lastname@example.org> 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?
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