Re: [PATCH 5/5] powerpc: Increase NR_IRQS Kconfig maximum to 32768

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Sun, 2010-01-31 at 22:14 +1100, Anton Blanchard wrote:
> With dynamic irq descriptors the overhead of a large NR_IRQS is much lower
> than it used to be. With more MSI-X capable adapters and drivers exploiting 
> multiple vectors we may as well allow the user to increase it beyond the
> current maximum of 512.
> 
> 32768 seems large enough that we'd never have to bump it again (although I bet
> my prediction is horribly wrong). It boot tests OK and the vmlinux footprint
> increase is only around 500kB due to:
> 
> struct irq_map_entry irq_map[NR_IRQS];

We could dynamically allocate that one.

Cheers,
Ben.

> We format /proc/interrupts correctly with the previous changes:
> 
>              CPU0       CPU1       CPU2       CPU3       CPU4       CPU5
>   286:          0          0          0          0          0          0     
>   516:          0          0          0          0          0          0     
> 16689:       1833          0          0          0          0          0     
> 17157:          0          0          0          0          0          0     
> 17158:        319          0          0          0          0          0     
> 25092:          0          0          0          0          0          0     
> 
> Signed-off-by: Anton Blanchard <anton@samba.org>
> ---
> 
> Index: linux-cpumask/arch/powerpc/Kconfig
> ===================================================================
> --- linux-cpumask.orig/arch/powerpc/Kconfig	2010-01-31 15:07:11.707211107 +1100
> +++ linux-cpumask/arch/powerpc/Kconfig	2010-01-31 21:52:39.999711689 +1100
> @@ -58,7 +58,7 @@ config IRQ_PER_CPU
>  
>  config NR_IRQS
>  	int "Number of virtual interrupt numbers"
> -	range 32 512
> +	range 32 32768
>  	default "512"
>  	help
>  	  This defines the number of virtual interrupt numbers the kernel