On Wed, 2009-10-14 at 12:59 -0600, Grant Likely wrote: > On Tue, Oct 13, 2009 at 11:44 PM, Michael Ellerman > <mich...@ellerman.id.au> wrote: > > The irq_desc array consumes quite a lot of space, and for systems > > that don't need or can't have 512 irqs it's just wasted space. > > > > The first 16 are reserved for ISA, so the minimum of 32 is really > > 16 - and no one has asked for more than 512 so leave that as the > > maximum. > > Does it really make sense to have this as a user twiddlable value? > Especially when many users just don't have the background to know what > an appropriate value is here and will get it wrong? I believe your > sparse IRQ patch has a bigger impact anyway on systems where memory is > tight.
We have users? But yes I think it's reasonable, there's a million other options people can fiddle with and break their kernel, I don't see that this is much different. The sparse IRQ patch has a bigger difference on the size of the irq_desc array, but there are still other things that are statically sized based on NR_IRQs. So if you're building an machine-specific kernel and you know you're only going to have N interrupts, then this will give you a bigger saving. But I'm not super fussed, if other people think it's too dangerous we can drop it. cheers
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