Re: [PATCH] local_irq_disable removal

From: Daniel Walker (dwalker_at_mvista.com)
Date: 06/11/05

  • Next message: Paul E. McKenney: "Re: Attempted summary of "RT patch acceptance" thread" 
    Date:	Sat, 11 Jun 2005 13:51:47 -0700 (PDT)
To: Ingo Molnar <mingo@elte.hu>

    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

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