https://bugs.dpdk.org/show_bug.cgi?id=749
Bug ID: 749
Summary: mlx5: ConnectX-6 not all missed packets accounted for
when using large maximum packet size
Product: DPDK
Version: unspecified
Hardware: x86
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: ethdev
Assignee: dev@dpdk.org
Reporter: martin.wei...@allegro-packets.com
Target Milestone: ---
Version: 21.05 (which is not available in the Bugzilla version field)
When testing with ConnectX-6 we recently became aware that a lot of missed
packets did not show up in the statistics.
After some further testing it looks like this is somehow related to using a
large maximum packet size (which I believe
makes the driver use a different scatter-gather receive path).
The following testpmd invocations can be used to demonstrate this behavior.
First an example for a "normal" run without the large maximum packet size:
./app/dpdk-testpmd -a c1:00.0 -a c1:00.1 -n 4 --legacy-mem --
--total-num-mbufs=2000000 --rx-offloads=0x2800 --mbuf-size=2331 --rxd=4096
The xstats for one port look like this:
rx_good_packets: 540138902
tx_good_packets: 537739805
rx_good_bytes: 298771912199
tx_good_bytes: 171950534158
rx_missed_errors: 572790
rx_errors: 0
tx_errors: 0
rx_mbuf_allocation_errors: 0
rx_q0_packets: 540138902
rx_q0_bytes: 298771912199
rx_q0_errors: 0
tx_q0_packets: 537739805
tx_q0_bytes: 171950534158
rx_wqe_errors: 0
rx_unicast_packets: 540711692
rx_unicast_bytes: 301254119575
tx_unicast_packets: 537739805
tx_unicast_bytes: 171950534158
rx_multicast_packets: 0
rx_multicast_bytes: 0
tx_multicast_packets: 0
tx_multicast_bytes: 0
rx_broadcast_packets: 0
rx_broadcast_bytes: 0
tx_broadcast_packets: 0
tx_broadcast_bytes: 0
tx_phy_packets: 537739805
rx_phy_packets: 540719221
rx_phy_crc_errors: 0
tx_phy_bytes: 174101493378
rx_phy_bytes: 301258662491
rx_phy_in_range_len_errors: 0
rx_phy_symbol_errors: 0
rx_phy_discard_packets: 7529
tx_phy_discard_packets: 0
tx_phy_errors: 0
rx_out_of_buffer: 0
tx_pp_missed_interrupt_errors: 0
tx_pp_rearm_queue_errors: 0
tx_pp_clock_queue_errors: 0
tx_pp_timestamp_past_errors: 0
tx_pp_timestamp_future_errors: 0
tx_pp_jitter: 0
tx_pp_wander: 0
tx_pp_sync_lost: 0
For this particular testcase the sum of rx_good_packets, rx_missed_errors and
rx_phy_discard_packets is always
the expected total packet count of 540719221.
If however testpmd is invoked like this:
./app/dpdk-testpmd -a c1:00.0 -a c1:00.1 -n 4 --legacy-mem --
--total-num-mbufs=2000000 --max-pkt-len=15360 --rx-offloads=0x2800
--mbuf-size=2331 --rxd=4096
The xstats after the testcase run look like this:
rx_good_packets: 521670616
tx_good_packets: 522641593
rx_good_bytes: 288980135079
tx_good_bytes: 167591285708
rx_missed_errors: 879662
rx_errors: 0
tx_errors: 0
rx_mbuf_allocation_errors: 0
rx_q0_packets: 521670616
rx_q0_bytes: 288980135079
rx_q0_errors: 0
tx_q0_packets: 522641593
tx_q0_bytes: 167591285708
rx_wqe_errors: 0
rx_unicast_packets: 522550278
rx_unicast_bytes: 291559156800
tx_unicast_packets: 522641593
tx_unicast_bytes: 167591285708
rx_multicast_packets: 0
rx_multicast_bytes: 0
tx_multicast_packets: 0
tx_multicast_bytes: 0
rx_broadcast_packets: 0
rx_broadcast_bytes: 0
tx_broadcast_packets: 0
tx_broadcast_bytes: 0
tx_phy_packets: 522641593
rx_phy_packets: 540719221
rx_phy_crc_errors: 0
tx_phy_bytes: 169681852080
rx_phy_bytes: 301258662491
rx_phy_in_range_len_errors: 0
rx_phy_symbol_errors: 0
rx_phy_discard_packets: 30665
tx_phy_discard_packets: 0
tx_phy_errors: 0
rx_out_of_buffer: 0
tx_pp_missed_interrupt_errors: 0
tx_pp_rearm_queue_errors: 0
tx_pp_clock_queue_errors: 0
tx_pp_timestamp_past_errors: 0
tx_pp_timestamp_future_errors: 0
tx_pp_jitter: 0
tx_pp_wander: 0
tx_pp_sync_lost: 0
The rx_good_packets, rx_missed_errors and rx_phy_discard_packets counters never
sum up to the expected packet
count:
521670616 + 879662 + 30665 = 522580943
540719221 - 522580943 = 18138278 (packets not accounted for)
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