Messages in this thread |  | | Date | Sun, 15 Sep 2002 07:51:39 -0400 (EDT) | From | Ingo Molnar <> | Subject | Re: [PATCH] per-interrupt stacks - try 2 |
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On Thu, 12 Sep 2002, David Howells wrote:
> > per-CPU per-IRQ i mean, of course. It's a basic performance issue, on > > SMP we do not want dirty IRQ stacks to bounce between CPUs ... > > Do you have benchmarks or something to show that is this actually a > _significant_ problem?
you need benchmarks to tell that pure per-IRQ stacks are bad for SMP performance?
per-IRQ+per-CPU and pure per-CPU IRQ stacks should perform rougly equally well on SMP - with per-CPU IRQ stacks having lower runtime setup cost.
> After all, unless you bind the interrupts to particular IRQs, loads of > data - including the irq_desc[] table - are going to be bouncing too.
there's a difference between bouncing 1-2 cachelines and bouncing a *full, dirtied stack*. The irq_desc[] bouncing is pretty much unavoidable (IRQs do need some global state) - the stack bouncing is just plain stupid and perfectly avoidable.
Ingo
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