What does "ca drop" and "resending" debug log mean?

[huzhijiang]

When doing perf test, we saw below logs, ands when this happend, ucx_perftest just stuck there without progress. does this mean we hit some bug or bottleneck?

Thanks!

[1714701098.262163] [host-192-168-20-64:664618:0]           ud_ep.c:92   UCX  DEBUG ep: 0x206fd50 ca drop@cwnd = 2 in flight: 1
[1714701098.262184] [host-192-168-20-64:664618:0]           ud_ep.c:1334 UCX  DEBUG ep(0x206fd50): resending rt_psn 1 rt_max_psn 1 acked_psn 0 max_psn 2 ack_req 1
[1714701098.262191] [host-192-168-20-64:664618:0]           ud_ep.c:1337 UCX  DEBUG ep(0x206fd50): resending completed
[1714701102.165000] [host-192-168-20-64:664618:0]           ud_ep.c:344  UCX  TRACE scheduling resend now: 668537073328058 last_send: 668528487124916 diff: 8586203142 tick: 250046700000
[1714701102.165043] [host-192-168-20-64:664618:0]           ud_ep.c:92   UCX  DEBUG ep: 0x206fd50 ca drop@cwnd = 2 in flight: 1
[1714701102.165061] [host-192-168-20-64:664618:0]           ud_ep.c:1334 UCX  DEBUG ep(0x206fd50): resending rt_psn 1 rt_max_psn 1 acked_psn 0 max_psn 2 ack_req 1
[1714701102.165067] [host-192-168-20-64:664618:0]           ud_ep.c:1337 UCX  DEBUG ep(0x206fd50): resending completed

[huzhijiang]

It seems it was caused by using wrong device, I will double check