Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domaind

Qais Yousef
2015-11-23T16:55:35Z

On 11/20/2015 08:39 PM, Thomas Gleixner wrote:
>> Same applies when doing the reverse mapping.
>>
>> In other words, the ipi_mask won't always necessarily be linear to facilitate
>> the 1:1 mapping that this approach assumes.
>>
>> It is a solvable problem, but I think we're losing the elegance that promoted
>> going into this direction and I think sticking to using struct ipi_mapping
>> (with some enhancements to how it's exposed an integrated by/into generic
>> code) is a better approach.
> The only reason to use the ipi_mapping thing is if we need non
> consecutive masks, i.e. cpu 5 and 9.

That's the case I had in mind.

>
> I really don't want to have it mandatory as it does not make any sense
> for systems where the IPI is a single per_cpu interrupt. For the
> linear consecutive space it is just adding memory and cache footprint
> for no benefit. Think about machines with 4k and more cpus ....

OK. Although so far I think the ovehead is higher without the
ipi_mapping because of all the extra checkings we have to do when
sending an IPI. I'll leave this to code review when I have something
ready though.

I'm debugging more problems and hopefully I'll send something this week.

Thanks,
Qais