iRDMA流量控制总结 - 5

6.0 Priority Flow Control – Verification带优先级的流量控制 - 验证

6.1  Priority Counters优先级计数器

Priority flow control counters for each interface are available in ethtool. They measure the number of Xon and Xoff (transmit on and off) frames sent and received by that interface. 每个接口的优先级流量控制计数器都在 ethtool 中提供。它们测量该接口发送和接收的 Xon 和 Xoff（发送开和关）帧的数量。

To view them: 验证它们

# ethtool -S | grep prio

Counters are named with tx/rx, priority number, and either xon or xoff. 计数器以 tx/rx、优先级编号以及 xon 或 xoff 命名。

For example:例如

# ethtool -S enp175s0f0 | grep prio tx_priority_0_xon.nic: 1 tx_priority_0_xoff.nic: 6434 tx_priority_1_xon.nic: 1 tx_priority_1_xoff.nic: 6434 tx_priority_2_xon.nic: 2 tx_priority_2_xoff.nic: 14864 tx_priority_3_xon.nic: 1 tx_priority_3_xoff.nic: 6434 tx_priority_4_xon.nic: 0 tx_priority_4_xoff.nic: 0 tx_priority_5_xon.nic: 1 tx_priority_5_xoff.nic: 6434 tx_priority_6_xon.nic: 1 tx_priority_6_xoff.nic: 6434 tx_priority_7_xon.nic: 1 tx_priority_7_xoff.nic: 6434 rx_priority_0_xon.nic: 0 rx_priority_0_xoff.nic: 0 rx_priority_1_xon.nic: 0 rx_priority_1_xoff.nic: 0 rx_priority_2_xon.nic: 0 rx_priority_2_xoff.nic: 0 rx_priority_3_xon.nic: 0 rx_priority_3_xoff.nic: 0 rx_priority_4_xon.nic: 0 rx_priority_4_xoff.nic: 0 rx_priority_5_xon.nic: 0 rx_priority_5_xoff.nic: 0 rx_priority_6_xon.nic: 0 rx_priority_6_xoff.nic: 0 rx_priority_7_xon.nic: 0 rx_priority_7_xoff.nic: 0

Note that the Rx counters all 0. 请注意，Rx 计数器全部为 0。

When adapters are connected through a switch, the rx_priority_* counters might be 0, indicating that the adapter has not received any pause frames from the switch. Depending on the level of stress in the network, this is acceptable if the switch has enough buffering to keep up with the host demand. However, for high stress traffic such as HPC applications at larger scale, often the switch sends pause frames to the host. In general, it is expected to see both tx and rx_priority counters. 当适配器通过交换机连接时，rx_priority_* 计数器可能为 0，表明适配器没有从交换机接收到任何暂停帧。根据网络压力的大小，如果交换机有足够的缓冲来满足主机需求，这种情况是可以接受的。但是，对于高压力流量（如大规模 HPC 应用），交换机通常会向主机发送暂停帧。一般来说，我们希望同时看到 tx 和 rx_priority 计数器。

Note that some of the Tx counters have the same value. 请注意，某些 Tx 计数器的值相同。

In the 800 Series QoS implementation, if PFC is enabled for any priority in a traffic class, all priorities in that traffic class get pause frames. This means that the counters for all priorities in the same TC are incremented in unison, regardless of the particular single priority that is causing PFC to trigger. If all priorities are mapped to the same TC, they all increment in unison. 在 800 系列 QoS 实施中，如果为流量类中的任何优先级启用了 PFC，则该流量类中的所有优先级都会获得暂停帧。这意味着，同一 TC 中所有优先级的计数器都会同步递增，而不管是哪个特定的单一优先级触发了 PFC。如果所有优先级都映射到同一 TC，则它们都会同步递增。

This implementation is in line with 802.1Q recommendations. 这一实施符合 802.1Q 建议。

• 802.1Q Section 37.3: NOTE 2 — All priorities within a traffic class typically share similar traffic handling requirements (e.g., loss a