[dpdk-dev] Packet drops at lower tc transmit-rates.
Sridhar.V.Iyer
sridhariyer at versa-networks.com
Thu Apr 7 21:24:04 CEST 2016
Hi all,
We are using DPDK 1.7 in our application.
We are running into an issue where a lower transmit-rate configured at the traffic class of a subport is causing complete packet drops.
Here are few parameters to clear up some context:
Packet length = 728 byte
Port rate = 1Gbps = 12500000 bytes/s
Subport tc_period = 10 ms
Configured TC0 rate = 500 kbps = 62500 bytes/s
This means that for the given subport tc0_credits_per_period = 10 * 62500 / 1000 = 625 (from rte_sched_subport_config)
Now, there is no token bucket at the subport-tc level, so there are no credits to accrue. The tc0_credits are just initialized to 625.
- This means that we’ll never have “enough_credits” in grinder_credits_check to process a 728 byte packet.
- grinder_schedule will then return 0.
- grinder_handle will return 0.
- which implies that the rte_sched_port_dequeue will never dequeue any packet.
- After port->time exceeds the subport->tc_time, tc0_credit will be re-initialized back to 625 again.
Is this a bug in the logic?
What are some of the viable workarounds?
Is this issue taken care of in the later releases?
Regards,
Sridhar V Iyer
<http://www.versa-networks.com/> <http://www.versa-networks.com/>
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