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    SubjectRe: question about the limited interrupt vector resource on a single cpu
    On Wed, 6 Jun 2018, Pingfan Liu wrote:
    > On Wed, Jun 6, 2018 at 5:34 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
    > > On Wed, 6 Jun 2018, Pingfan Liu wrote:
    > >
    > >> On Wed, Jun 6, 2018 at 5:15 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
    > >> > On Wed, 6 Jun 2018, Pingfan Liu wrote:
    > >> >
    > >> >> For x86, there is around 200 vectors left for external device on a
    > >> >> single logic cpu.
    > >> >>
    > >> >> Is there any case that we exhaust them in real world, and is it worth to fix?
    > >> >
    > >> > Exhaustion is unlikely, but how would you fix it? The vector space per CPU
    > >> > is limited by hardware not software.
    > >> >
    > >> Playing some trick on iommu, we can use it to identify the irq requester.
    > >
    > > But what's the point? If you have more than 200 device interrupts on a
    > > single CPU, then you surely have other problems than that.
    > >
    > > What kind of problem are you trying to solve?
    > >
    > In kdump case, normally we set nr_cpus=1 by default, and in some huge
    > system, it can exhaust vector space.

    Well. For kdump it's really not necessary to initialize all devices. So
    this is more a configuration problem.

    > By this is easily to resolve by inc nr_cpus. Hence I post this
    > question to see whether there are other requirements to resolve such
    > case

    Not really. We've covered a lot of the issues with multi-queue devices and
    suspend, where you can run into the same issue, via the managed interrupt
    infrastructure.

    Thanks,

    tglx

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