Re: [PATCH] sparse_irq aka dyn_irq v13

[Yinghai Lu <yinghai@kernel.org>]

Benjamin Herrenschmidt wrote:
> 
> In any case, the patch is too big and unless I missed something, totally
> under-documented in what it does, why it does it, how it does it, etc...
> with a bit more of that, I might take more time to look closely and find
> out that indeed it's something I can make use of, maybe with a few
> tweaks.

will cut it to smaller ones. try to have one big one to make review more easy.

starting case
1. IBM x3950 have io apic pins > 224?
2. SGI big box need 8192 irqs 

want to make same kernel with NR_CPUS = 4096 can be used with regular sized system.

points are
1. removing irq_desc array and NR_IRQS. for small system will have less wasting ram in that array, and for big system will get more irqs like system have 8 pcie cards and every card need 40 MSI vector or a lot of IO apic controllers etc.
2. make irq number is bus/devfn/idx, and every dev func will use 12bit range, irq number is relatively fixed not like current MSI irq creating is some kind of floating from NR_IRQS too. 
3. irq_desc is going with /proc/irq/xxx/smp_affinity.

YH