Q-Logic 8100 SERIES manual Receive Side Scaling Concepts

6–Configuring NIC Functionality in the Converged Network Adapter Configuring the NIC in a Windows Environment

about the CheckSumOffload parameter, refer to Table 6-1Do not turn off checksum offload unless you are debugging a checksum computation problem. TCP checksum offloading significantly reduced reduces host CPU use when using jumbo frames.

Stateless offload—QLogic 8100 Series Adapters support large send offloading (LSO).LSO enables the Microsoft Windows TCP stack to send one large block of data to the QLogic adapter, which then segments this large block into multiple TCP packets. The LargeSendOffloadSupport parameter is enabled by default and can be disabled on the Windows Advanced property pages for the QLogic 10Gb PCI Ethernet adapter using Windows Device Manager. For information about the LargeSendOffloadSupport parameter, refer to Table 6-1.

Receive Side Scaling

QLogic 8100 Series Adapters supports receive side scaling (RSS) in Microsoft Windows environments for nonoffloaded IP/TCP traffic. When a packet arrives on a network interface, an interrupt is sent to the network driver. The network driver then executes a deferred procedure call (DPC), which runs on the same CPU as the interrupt. With RSS disabled, only one DPC can execute at a time. With RSS enabled, up to four parallel DPCs can run on four different processors or cores, which enables the simultaneous receive processing of incoming packets (Figure 6-4).

Figure 6-4. Receive Side Scaling Concepts

With RSS enabled, the NIC driver implements a hash function to distribute inbound packets across CPUs. In-order delivery is maintained by identifying the flow. RSS provides the following advantages:

Parallel processing of inbound packets while maintaining in-order delivery

Load balancing of network processing across CPUs in an symmetrical multiprocessing (SMP) system

Cache locality

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