Re: [dpdk-dev] [PATCH v2 2/3] net/af_xdp: support pinning of IRQs

["Varghese, Vipin" <vipin.varghese@intel.com>]

Hi Bruce,

snipped
> > >
> > > For the no-pinning case, all IRQs are landing on the default core 0,
> > > which results in very poor scaling versus the pinned case where scaling is
> linear.
> >
> > Thanks for the information, but a question here `Is the reason for
> > landing all IRQ on core '0' is because the Kernel CMD line 'isol or no
> > interupts' is done for all expect core 0?`
> >
> > If the cores are not isolated and no interrupts are redirected; normally `cat
> /proc/interrupts` shows IRQ mask to cores. Depending upon FDIR (intel X522
> and X710) this could be core 0 or 'n-1'?
> >
> Yes, the interrupt pinning default is somewhat dependent on the exact setup,
> but the fact remains that in just about any setup the interrupts for an AF_XDP
> queue are unlikely to end up on the exactly the one core that the user wants
> them on. This is what makes this patch so necessary, both from a usability and
> performance point of view.
> 
> In the absense of alternatives, I really think this patch should be merged, since
> with more than one point the difference between having correctly or
> incorrectly pinned interrupts is huge. I'd also point out that in my testing the
> interrupts need to be pinned each and every time an app is run - it's not a set
> once and forget thing.
Yes, I agree with you as in my testing with XDP and FDIR we had to do this in each test run.

 This ability to have the driver pin the interrupts for the
> user would be a big timesaver for developers too, who may be constantly re-
> running apps when testing.
Here my understanding, user can not or should not pass DPDK cores for interrupt pinning. So should we ask the driver to fetch `rte_eal_configuration` and ensure the same?

> 
> Regards,
> /Bruce