The rx-queue to CPU affinity you're referring to should remain fairly static if the packets are getting processed fast enough. If you are interested in controlling this behavior you can manipulate receive flow hash indirection tables (ethtool - x) , irq affinities (/proc/interrupts/$irq/smp_affinity) or configure relevant stack if you're using solarflare (through onload profile).
Hope this helps. On Fri, 15 Mar 2019, 14:40 Peter Veentjer, <[email protected]> wrote: > I have a question about RSS and how a CPU is selected to process the > interrupt. > > So with RSS you have multiple rx-queue and each rx-queue has an IRQ > associated to it. Each CPU can pick up the IRQ as clearly explained here: > > https://www.kernel.org/doc/Documentation/networking/scaling.txt > > It is possible to using IRQ/CPU affinity to prevent that just any CPU > picking up the IRQ. > > My question is about the default behavior when no explicit affinity has > been set. > > Is there any advantage of letting the same rx-queue being processed by > different CPU's? In case of a random CPU picking up same IRQ, you could end > a packet being processed at a different CPU for every packet being > received. This will cause a lot of cache coherence traffic which will > certainly not improve performance. > > When I look at /proc/interrupts of my local system, it seems the same CPU > is processing a specific rx-queue. So it looks that the OS is already > applying some form of affinity to map an IRQ to a CPU. > > Can someone shed a light on this? > > Thanks. > > > -- > You received this message because you are subscribed to the Google Groups > "mechanical-sympathy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "mechanical-sympathy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
