Re: [PATCH] CHECK_IRQ_PER_CPU() to avoid dead code in __do_IRQ()

On Mon, 8 Aug 2005, Alexander Nyberg wrote:

> > IRQ_PER_CPU is not used by all architectures.
> > This patch introduces the macros
> > ARCH_HAS_IRQ_PER_CPU and CHECK_IRQ_PER_CPU() to avoid the generation of
> > dead code in __do_IRQ().
> > 
> > ARCH_HAS_IRQ_PER_CPU is defined by architectures using
> > IRQ_PER_CPU in their
> >         include/asm_ARCH/irq.h
> > file.
> > 
> > Through grepping the tree I found the following
> > architectures currently use IRQ_PER_CPU:
> > 
> >         cris, ia64, ppc, ppc64 and parisc. 
> > 
> 
> There are many places where one could replace run-time tests with 
> #ifdef's but it makes reading more difficult (and in longer terms
> maintainence). Have you benchmarked any workload that benefits 
> from this?

I doubt you'd be able to collect convincing benchmark data, but skipping a 
branch (possibly mispredicted) is worth it IMO.
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---

• References:
  • [PATCH] CHECK_IRQ_PER_CPU() to avoid dead code in __do_IRQ()
    • From: Karsten Wiese <[email protected]>
  • Re: [PATCH] CHECK_IRQ_PER_CPU() to avoid dead code in __do_IRQ()
    • From: Alexander Nyberg <[email protected]>

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