Re: [patch 00/47] Sparse irq rework

[Ingo Molnar]

* Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:

> Looking at this objectively I see a bitmap sized to the formula 
> 32*NR_CPUS with NR_CPUS expected to double every 18-24 months. Which 
> means in a decade our worst case will be 2M not 64k.

On a 16 TB box? Noise.

> Can we please build this with scalable interfaces so we don't have to 
> do this again in a couple of years, and so we don't have to have 
> little machines paying the price for big machines, and so that big 
> machines aren't hamstrung because of data structures built for little 
> machines.

Bitmaps are rather scalable, we use them all around the place.

> Perhaps this just requires using ida instead of a bitmap.

Erm, IDA/IDR uses a bitmap ...

IDA is a dynamically allocated bitmap - but for something as critical as 
IRQs i'd rather like to see a preallocated bitmap and platform control 
over the max (nr_irqs). We dont want to allow crappy drivers to install 
irq 0x12345678 and blow up the bitmap size to dozens of MB, etc.

Bitmaps are simple - and that's a virtue.

Thanks,

	Ingo
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