I'm picking up the request 'Setting RPS affinities from network driver' from Sunil Kovvuri http://marc.info/?t=142424023500001&r=1&w=2 as I assume to have the same issue here.
When receiving CAN frames from a specific CAN network interface (e.g. can0) the frames are sporadically out-of-order on SMP systems like my Core i7 laptop with 4 CPUs. This out-of-order reception kills reliable communication e.g. for CAN transport protocols. First approach was to set the smp_affinity for the USB adapter on irq 28 with: echo 1 > /proc/irq/28/smp_affinity This worked in my case but it looks wrong to pin the USB host adapter to a single CPU and has to be done by hand depending on where the CAN interfaces are attached to the system. Next idea was to use RPS after reading Documentation/networking/scaling.txt As the only relevant flow identifiction is the number of the incoming CAN interface I added skb_set_hash(skb, dev->ifindex, PKT_HASH_TYPE_L2); when creating CAN skbs with alloc_can_skb() in drivers/net/can/dev.c After enabling RPS for my four CPUs with echo f > /sys/class/net/can0/queues/rx-0/rps_cpus I had no more out-of-order frames in my system :-) My two questions: 1. Is there any better solution to meet the described requirements? 2. If not: How can enable this RPS solution by default for CAN interfaces? Best regards, Oliver -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html