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

From	Qais Yousef <qais.yousef@imgtec.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domaind
Date	2015-11-23 18:00 +0100
Message-ID	<qy2D8-4un-5@gated-at.bofh.it> (permalink)
References	(2 earlier) <qsd8e-3Cy-7@gated-at.bofh.it> <qsSEq-5Hy-3@gated-at.bofh.it> <qvvBE-1Ii-11@gated-at.bofh.it> <qwRqp-63H-7@gated-at.bofh.it> <qx0N3-3MB-15@gated-at.bofh.it>
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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
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Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domain Thomas Gleixner <tglx@linutronix.de> - 2015-11-16 18:20 +0100
  Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domain Qais Yousef <qais.yousef@imgtec.com> - 2015-11-17 11:10 +0100
    Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domain Thomas Gleixner <tglx@linutronix.de> - 2015-11-17 11:20 +0100
      Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domain Qais Yousef <qais.yousef@imgtec.com> - 2015-11-17 11:40 +0100
  Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domain Qais Yousef <qais.yousef@imgtec.com> - 2015-11-20 11:50 +0100
    Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domaind Thomas Gleixner <tglx@linutronix.de> - 2015-11-20 21:50 +0100
      Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domaind Qais Yousef <qais.yousef@imgtec.com> - 2015-11-23 18:00 +0100

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