Re: [PATCH] i386 irq: Kill NR_IRQ_VECTORS and increase NR_IRQS

From: Eric W. Biederman
Date: Fri Feb 16 2007 - 05:36:24 EST

Andi Kleen <ak@xxxxxxx> writes:

>> Allowing the kernel to work on big machines without complicated
>> and error prone irq remapping logic.
> How much memory does this use by default? If it's much there should
> be at least a CONFIG_* to make it smaller.

If you don't build a generic kernel and are not a big way smp you only
get 200 IRQs so it is less.

Otherwise it is either 1024 or NR_CPUS*32 depending on the subarch
we compile. The limits are actually unchanged from what we are doing

I'm in the final stages of figuring out how to kill the stupid
irq_desc array which should make all the memory consumption worries
go away but that is a little ways off, and I'm putting real bug
fixes ahead of that work.

Basically this is just a back port from x86_64 without the
complication of the per cpu vector logic. So if we run into any
issues I missed before this reaches a stable kernel we can just copy
the fix from x86_64 where we have been doing this for a while.

So in short the existing CONFIG_ options should give us the control
we need, and before it becomes any kind of an issue I intend to
completely remove the compile time limit and make it dynamic.

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