[illumos-Developer] Available MSI(-x) interrupt limit.

[Craig Morgan]

I think its the below you are thinking of …

    set ddi_msix_alloc_limit=8
    * set pcplusmp:apic_msix_max=8

Which is very useful, particularly for 10GbE adapters which have a high
number of DMA per port (most Intels are 8), so increasing the above over
the default of 2 spreads the work around nicely amongst cores.

— Craig Morgan

On 7 Jun 2011, at 15:51, Garrett D'Amore wrote:

> Yes.    The limit comes from the fact that ill behaved devices/drivers could easily consume all the interrupts on a system, preventing other devices from attaching.  There was a recent rearchitecture of the interrupt code specifically for MSI-X that offers far more interrupt vectors to devices, in exchange for the device registering a callback indicating a willingness to return interrupts back to the system when they become scarce.
> 
> There's also a legacy override somewhere that you can use for specific devices, but it isn't documented.  I don't remember the name of the override, but it can grow the set up to 8.
> 
>  -- Garrett D'Amore
> 
> On Jun 7, 2011, at 5:49 PM, "Alexey Zaytsev" <alexey.zaytsev at gmail.com> wrote:
> 
>> Hey.
>> 
>> Any ideas, what's the reason to have the 2 msi per device limit?
>> It's been there from the start of the history.
>> 
>> https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/os/ddi_intr_impl.c#L296
>> https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/os/ddi_intr_impl.c#L40
>> https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/sys/ddi_intr_impl.h#L146
>> 
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