[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCHv1] xen: increase default number of PIRQs for hardware domains
On 05/12/14 09:44, Jan Beulich wrote: >>>> On 03.12.14 at 17:04, <david.vrabel@xxxxxxxxxx> wrote: >> The default limit for the number of PIRQs for hardware domains (dom0) >> is not sufficient for some (x86) systems. >> >> Since the pirq structures are individually and dynamically allocated, >> the limit for hardware domains may be increased to the number of >> possible IRQs. > > I nevertheless disagree to moving the bound up to the Xen internal > limit unconditionally: What use does it have to allow hwdom to use > thousands of MSIs? If a system got that many, the main purpose of > running Xen on it I would expect to be to hand various of the > respective devices to guests. Hence no need for hwdom to have > that many by default, even if this doesn't result in any extra > resource consumption. > > That said, I can see the current default of 256 being too low though. > Quite likely in the absence of a user specified value the default > ought to be derived from nr_irqs - nr_static_irqs rather than being > any fixed number. Considering the default used for nr_irqs, I'd think > along the lines of sqrt(num_present_cpus()) * NR_DYNAMIC_VECTORS > or dom0->max_vcpus * NR_DYNAMIC_VECTORS (or the minimum of > the two) for x86. The reason for a non obvious default like this would need a comment and I can't write one because I can't see a reason for it. Perhaps if you write a suitable comment for your preferred default I can respin this patch? David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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