Re: kern/55567: tcp-send slows down to slow single byte transfers

[Frank Kardel <kardel%netbsd.org@localhost>]

Here is some information on the state when we are in the slowed down mode:

Connection: (netstat -Ana | grep 65454
ffffd17391db63a8 tcp        0      0 127.0.0.1.5433 
127.0.0.1.65454       ESTABL
ffffd17391db6060 tcp        0    163 127.0.0.1.65454 
127.0.0.1.5433        ESTABL

Server side TCP-PCB:
TCP Protocol Control Block at 0xffffd17391db63a8:

Timers:
        REXMT   0x100<MPSAFE>
        PERSIST 0x100<MPSAFE>
        KEEP    0x102<PENDING,MPSAFE>   719818
        2MSL    0x100<MPSAFE>


State: ESTABLISHED, flags 0x9e4, inpcb 0xffffd17355b48c70, in6pcb 0x0

rxtshift 0, rxtcur 3, dupacks 0
peermss 33584, ourmss 33584, segsz 20480, segqlen 0

snd_una 72877108, snd_nxt 72877108, snd_up 72877108
snd_wl1 2183613798, snd_wl2 72877023, iss 2198870750, snd_wnd 32768

rcv_wnd 32768, rcv_nxt 2183614269, rcv_up 2183613798, irs 2183533130

rcv_adv 2183647037, snd_max 72877108, snd_cwnd 78135, snd_ssthresh 536854528
rcvtime 43067, rtttime 0, rtseq 72877023, srtt 14, rttvar 9, rttmin 2, 
max_sndwnd 32768

oobflags 0, iobc 0, softerror 0

snd_scale 3, rcv_scale 3, req_r_scale 3, req_s_scale 3
ts_recent 2123, ts_regent_age 43067, last_ack_sent 2183614269

Client side TCP_PCB:
TCP Protocol Control Block at 0xffffd17391db6060:

Timers:
        REXMT   0x100<MPSAFE>
        PERSIST 0x102<PENDING,MPSAFE>   57
        KEEP    0x102<PENDING,MPSAFE>   719552
        2MSL    0x100<MPSAFE>


State: ESTABLISHED, flags 0xbe4, inpcb 0xffffd17355b48b80, in6pcb 0x0

rxtshift 0, rxtcur 3, dupacks 0
peermss 33584, ourmss 33584, segsz 16384, segqlen 0

snd_una 2183614282, snd_nxt 2183614282, snd_up 2183614281
snd_wl1 2199032056, snd_wl2 2183579549, iss 2183533130, snd_wnd 0

rcv_wnd 32768, rcv_nxt 72877108, rcv_up 2199032056, irs 2198870750

rcv_adv 72909876, snd_max 2183614282, snd_cwnd 32769, snd_ssthresh 536854528
rcvtime 43198, rtttime 0, rtseq 2183613798, srtt 32, rttvar 3, rttmin 2, 
max_sndwnd 32768

oobflags 0, iobc 0, softerror 0

snd_scale 3, rcv_scale 3, req_r_scale 3, req_s_scale 3
ts_recent 2254, ts_regent_age 43198, last_ack_sent 72877108

Current packet trace:
14:40:25.770035 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 
2183614290:2183614291, ack 72877108, win 4096, options [nop,nop,TS val 
2343 ecr 2334], length 1
14:40:25.970039 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 1, 
win 4096, options [nop,nop,TS val 2344 ecr 2343], length 0
14:40:30.770195 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 1:2, 
ack 1, win 4096, options [nop,nop,TS val 2353 ecr 2344], length 1
14:40:30.970199 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 2, 
win 4096, options [nop,nop,TS val 2354 ecr 2353], length 0
14:40:35.770256 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 2:3, 
ack 1, win 4096, options [nop,nop,TS val 2363 ecr 2354], length 1
14:40:35.970358 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 3, 
win 4096, options [nop,nop,TS val 2364 ecr 2363], length 0
14:40:40.770512 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 3:4, 
ack 1, win 4096, options [nop,nop,TS val 2373 ecr 2364], length 1
14:40:40.970516 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 4, 
win 4096, options [nop,nop,TS val 2374 ecr 2373], length 0
14:40:45.770674 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 4:5, 
ack 1, win 4096, options [nop,nop,TS val 2383 ecr 2374], length 1
14:40:45.970676 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 5, 
win 4096, options [nop,nop,TS val 2384 ecr 2383], length 0
14:40:50.770831 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 5:6, 
ack 1, win 4096, options [nop,nop,TS val 2393 ecr 2384], length 1
14:40:50.970837 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 6, 
win 4096, options [nop,nop,TS val 2394 ecr 2393], length 0
14:40:55.770990 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 6:7, 
ack 1, win 4096, options [nop,nop,TS val 2403 ecr 2394], length 1
14:40:55.970977 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 7, 
win 4096, options [nop,nop,TS val 2404 ecr 2403], length 0
14:41:00.771132 IP 127.0.0.1.65454 > 127.0.0.1.5433: Flags [.], seq 7:8, 
ack 1, win 4096, options [nop,nop,TS val 2413 ecr 2404], length 1
14:41:00.971155 IP 127.0.0.1.5433 > 127.0.0.1.65454: Flags [.], ack 8, 
win 4096, options [nop,nop,TS val 2414 ecr 2413], length 0