Enabling Linux Network Support of Hardware Multiqueue Devices

In the Linux kernel network subsystem, the Tx/Rx SoftIRQ and Qdisc are the connectors between the network stack and the net devices. A design limitation is that they assume there is only a single entry point for each Tx and Rx in the underlying hardware. Although they work well today, they won't in the future. Modern network devices (for example, E1000 and IPW2200) equip two or more hardware Tx queues to enable transmission parallelization or MAC-level QoS. These hardware features cannot be supported easily with the current network subsystem.

This paper describes the design and implementation for the network multiqueue patches submitted to netdev and LKML mailing lists early this year, which involved the changes for the network scheduler, Qdisc, and generic network core APIs. It will also discuss breaking the netdev->queue_lock with finegrained per-queue locks in the future. At the end of the paper, it takes the IPW2200 and E1000 drivers as an example to illustrate how the new network multiqueue features will be used by the network drivers.

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