Re: [PATCH] sparse_irq aka dyn_irq v13

[Mike Travis <travis@sgi.com>]

Andrew Morton wrote:
> On Thu, 13 Nov 2008 14:41:36 -0800
> Yinghai Lu <yinghai@kernel.org> wrote:
> 
>> Andrew Morton wrote:
>>
>>>> ...
>>>>
>>>>>> +static unsigned int kstat_irqs_legacy[NR_IRQS_LEGACY][NR_CPUS];
>>>>> Do these need to be 32-bit?  Maybe they'll fit in 16-bit, dunno.
>>>>>
>>>> struct irq_desc {
>>>>         unsigned int            irq;
>>>> #ifdef CONFIG_SPARSE_IRQ
>>>>         struct list_head        list;
>>>>         struct list_head        hash_entry;
>>>>         struct timer_rand_state *timer_rand_state;
>>>>         unsigned int            *kstat_irqs;
>>> That doesn't address my question.
>>>
>>> The above array can be very large.  Can we halve its size by using
>>> 16-bit quantities?  Will this code ever encounter IRQ numbers larger
>>> than 65536?
>>>
>> NR_CPUS=4096, NR_IRQS_LEGACY=16, and that array will be 256k bytes
>>
>> later could change that alloc_bootmem, so NR_CPUS will be replaced to nr_cpu_ids
> 
> Do the entries in that array need to be 32-bit?

That's a good question.  If there are 4k or 16k cpus, would the number of
irq's being "kstat'd" need to be > 64k?  (I'm not exactly sure why there
are NR_CPUS * NR_IRQS_LEGACY kstat entries per IRQ?)