On Sun, 2008-20-07 at 10:25 -0700, David Miller wrote: > They tend to implement round-robin or some similar fairness algorithm > amongst the queues, with zero concern about packet priorities. pfifo_fast would be a bad choice in that case, but even a pfifo cannot guarantee proper RR because it would present packets in a FIFO order (and example the first 10 could go to hardware queue1 and the next to hardware queue2). My view: i think you need a software queue per hardware queue. Maybe even these queues residing in the driver; that way you take care of congestion and it doesnt matter if the hardware is RR or strict prio (and you dont need the pfifo or pfifo_fast anymore). The use case would be something along: packets comes in, you classify find its for queue1, grab the per-hardware-queue1 lock, find the hardware queue1 is overloaded and stash it instead in s/ware queue1. If it wasnt congested, it would go on hardware queue1. When hardware queue1 becomes available and netif-woken, you pick first from s/ware queue1 (and batching could apply cleanly here) and send them to hardware queue. > It really is just like a bunch of queues to the phsyical layer, > fairly shared. I am suprised prioritization is not an issue. [My understanding of the intel/cisco datacentre cabal is they serve virtual machines using virtual wires; i would think in such scenarios youd have some customers who pay more than others]. > These things are built for parallelization, not prioritization. Total parallelization happens in the ideal case. If X cpus classify packets going to X different hardware queueus each CPU grabs only locks for that hardware queue. In virtualization, where only one customer's traffic is going to a specific hardware queue, things would work well. Non-virtualization scenario may result in collision in which two or more CPUs may contend for the same hardware queue (either transmitting or netif-waking etc). cheers, jamal -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
