29. Ethernet Link Flow Control Tests¶
The support of Ethernet link flow control features by Poll Mode Drivers consists in:
- At the receive side, if packet buffer is not enough, NIC will send out the pause frame to peer and ask the peer to slow down the Ethernet frame # transmission.
- At the transmit side, if pause frame is received, NIC will slow down the Ethernet frame transmission according to the pause frame.
MAC Control Frame Forwarding consists in:
- Control frames (PAUSE Frames) are taken by the NIC and do not pass to the host.
- When Flow Control and MAC Control Frame Forwarding are enabled the PAUSE frames will be passed to the host and can be handled by testpmd.
Note: Priority flow control is not included in this test plan.
Note: the high_water, low_water, pause_time, send_xon are configured into the NIC register. It is not necessary to validate the accuracy of these parameters. And what change it can cause. The port_id is used to indicate the NIC to be configured. In certain case, a system can contain multiple NIC. However the NIC need not be configured multiple times.
29.1. Prerequisites¶
Assuming that ports 0 and 2 are connected to a traffic generator,
launch the testpmd with the following arguments:
./build/app/testpmd -cffffff -n 3 -- -i --burst=1 --txpt=32 \
--txht=8 --txwt=0 --txfreet=0 --rxfreet=64 --mbcache=250 --portmask=0x5
The -n command is used to select the number of memory channels. It should match the number of memory channels on that setup.
If using vfio the kernel must be >= 3.6+ and VT-d must be enabled in bios.When using vfio, use the following commands to to load the vfio driver and bind it to the device under test:
modprobe vfio
modprobe vfio-pci
usertools/dpdk-devbind.py --bind=vfio-pci device_bus_id
29.2. Test Case: test_perf_flowctrl_on_pause_fwd_on¶
testpmd> set flowctrl rx on tx on high_water low_water pause_time
send_xon mac_ctrl_frame_fwd on autoneg on port_id
Setup the csum forwarding mode:
testpmd> set fwd csum
Set csum packet forwarding mode
Start the packet forwarding:
testpmd> start
csum packet forwarding - CRC stripping disabled - packets/burst=32
nb forwarding cores=1 - nb forwarding ports=10
RX queues=1 - RX desc=128 - RX free threshold=64
RX threshold registers: pthresh=8 hthresh=8 wthresh=4
TX queues=1 - TX desc=512 - TX free threshold=0
TX threshold registers: pthresh=32 hthresh=8 wthresh=8
Validate the NIC can generate the pause frame? Configure the traffic generator to send IPv4/UDP packet at the length of 66Byte at the line speed (10G). Because the 66Byte packet cannot reach line rate when running with testpmd, so it is expected that the pause frame will be sent to the peer (traffic generator). Ideally this mechanism can avoid the packet loss. And this depends on high_water/low_water and other parameters are configured properly. It is strongly recommended that the user look into the data sheet before doing any flow control configuration. By default, the flow control on 10G is disabled. the flow control for 1G is enabled.
Validate the NIC can deal with the pause frame. Configure the traffic generator to send out large amount of pause frames, this will cause the NIC to disable / slow down the packet transmission according to the pause time. Once the traffic generator stop sending the pause frame, the NIC will restore the packet transmission to the expected rate.
29.3. Test Case: test_perf_flowctrl_on_pause_fwd_off¶
testpmd> set flowctrl rx on tx on high_water low_water pause_time
send_xon mac_ctrl_frame_fwd off autoneg on port_id
Validate same behavior as test_perf_flowctrl_on_pause_fwd_on
29.4. Test Case: test_perf_flowctrl_rx_on¶
testpmd> set flowctrl rx on tx on high_water low_water pause_time
send_xon mac_ctrl_frame_fwd off autoneg on port_id
Validate same behavior as test_perf_flowctrl_on_pause_fwd_on
29.5. Test Case: test_perf_flowctrl_off_pause_fwd_off¶
This is the default mode for 10G PMD, by default, testpmd is running on this mode. no need to execute any command:
testpmd> set flowctrl rx off tx off high_water low_water pause_time
send_xon mac_ctrl_frame_fwd off autoneg on port_id
Validate the NIC won’t generate the pause frame when the packet buffer is not enough. Packet loss can be observed. Validate the NIC will not slow down the packet transmission after receiving the pause frame.
29.6. Test Case: test_perf_flowctrl_off_pause_fwd_on¶
testpmd> set flowctrl rx off tx off high_water low_water pause_time
send_xon mac_ctrl_frame_fwd on autoneg on port_id
Validate same behavior as test_perf_flowctrl_off_pause_fwd_off
29.7. Test Case: test_perf_flowctrl_tx_on¶
testpmd> set flowctrl rx off tx on high_water low_water pause_time
send_xon mac_ctrl_frame_fwd off autoneg on port_id
Validate same behavior as test_perf_flowctrl_on_pause_fwd_off