Messages in this thread | | | Date | Wed, 6 Jun 2018 14:08:45 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: question about the limited interrupt vector resource on a single cpu |
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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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