Re: [PATCH 0/8] tip related: radix tree for spareseirq and logical flat clean up

[Eric W. Biederman]

Yinghai Lu <yinghai@xxxxxxxxxx> writes:

> ---------spareirq radix tree related ----------------
> 94007e8: irq: remove not need bootmem code
> 4b0d3fa: radix: move radix init early
> 56af1a9: sparseirq: change irq_desc_ptrs to static
> b236235: sparseirq: use radix_tree instead of ptrs array
> 5918787: x86: remove arch_probe_nr_irqs
>
> so could reduce nr_irqs limitation for bunch ixgbe...
>
> ---------------x86 logical flat related -----------
> f5954c4: use nr_cpus= to set nr_cpu_ids early
> 7b8d6a9: x86: use num_processors for possible cpus
> d79d1de: x86: make 32bit apic flat to physflat switch like 64bit

Thanks for keeping this work alive.

I just skimmed through do_IRQ and I happened to notice that
we have an unnecessary inefficiency that using a radix tree for
irq_to_desc will magnify.

handle_irq should take an struct irq_desc * instead of a unsigned int irq.

and the per cpu vector_irq array should become a per cpu vector_desc array.

As soon as irq_to_desc is more than &irq_desc[irq] this saves us work
and cache line misses  at the cost of a simple code cleanup.


Eric
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