Re: [PATCH] x86_64: Restore the proper NR_IRQS define so larger systemswork.

[Jeremy Fitzhardinge]

Eric W. Biederman wrote:
> Xen pv 64 will work at least as well with a larger definition for
> NR_IRQS as it will work with a smaller definition, and since
> NR_VECTORS is 256 we always have more irqs with the 32bit definition
> we were mistakenly using. 
>
> Xen has 1024 event channels so I expect 1024 would the nice number to
> provide there.
>   

Yes, but really its overkill.  It needs about 6 interrupts/cpu for 
normal system overhead (timer, IPI, things like that), and then some 
amount for virtual devices.

dom0 - the control domain - will need some number of events per other 
guest domain, so it can start feeling the pressure depending on how many 
domains and devices there are.

   J
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