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

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR kern/55567; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/55567: tcp-send slows down to slow single byte transfers
Date: Fri, 14 Aug 2020 01:17:30 +0000

 Not sent to gnats.
 
    ------
 
 From: Frank Kardel <kardel%netbsd.org@localhost>
 To: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
 Subject: Re: kern/55567: tcp-send slows down to slow single byte transfers
 Date: Thu, 13 Aug 2020 14:44:56 +0200
 
 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