kern/97116: sis(4): low TCP throughput and abnormal delays with manual media selection

[Joseph Terner]

>Number:         97116
>Category:       kern
>Synopsis:       sis(4): low TCP throughput and abnormal delays with manual media selection
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu May 11 02:40:09 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Joseph Terner
>Release:        5.4-RELEASE
>Organization:
>Environment:
FreeBSD xylex 5.4-RELEASE-p1 FreeBSD 5.4-RELEASE-p1 #0: Wed May 18 02:50:23 CEST 2005     root at xylex:/usr/obj/usr/src/sys/GENERIC  i386

>Description:
dmesg(8) output:
sis0: <SiS 900 10/100BaseTX> port 0xdc00-0xdcff mem 0xcfffd000-0xcfffdfff irq 10 at device 3.0 on pci0
miibus0: <MII bus> on sis0
rlphy0: <RTL8201L 10/100 media interface> on miibus0
rlphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto

Using manual media selection (100baseTX/FDX) causes TCP throughput to drop to about 1-5 MBit/s. There seems to be no packet-loss, but abnormal delays show up if the host is pinged during the TCP transfer:

PING 192.168.5.6 (192.168.5.6): 56 data bytes
64 bytes from 192.168.5.6: icmp_seq=0 ttl=64 time=0.174 ms
64 bytes from 192.168.5.6: icmp_seq=1 ttl=64 time=0.170 ms
64 bytes from 192.168.5.6: icmp_seq=2 ttl=64 time=0.195 ms
64 bytes from 192.168.5.6: icmp_seq=3 ttl=64 time=29.269 ms
64 bytes from 192.168.5.6: icmp_seq=4 ttl=64 time=0.164 ms
64 bytes from 192.168.5.6: icmp_seq=5 ttl=64 time=0.193 ms
64 bytes from 192.168.5.6: icmp_seq=6 ttl=64 time=629.664 ms
64 bytes from 192.168.5.6: icmp_seq=7 ttl=64 time=0.189 ms
64 bytes from 192.168.5.6: icmp_seq=8 ttl=64 time=0.168 ms
64 bytes from 192.168.5.6: icmp_seq=9 ttl=64 time=0.189 ms
64 bytes from 192.168.5.6: icmp_seq=10 ttl=64 time=709.360 ms
64 bytes from 192.168.5.6: icmp_seq=11 ttl=64 time=0.213 ms
64 bytes from 192.168.5.6: icmp_seq=12 ttl=64 time=0.192 ms
64 bytes from 192.168.5.6: icmp_seq=13 ttl=64 time=489.767 ms
64 bytes from 192.168.5.6: icmp_seq=14 ttl=64 time=989.519 ms
64 bytes from 192.168.5.6: icmp_seq=15 ttl=64 time=0.192 ms
64 bytes from 192.168.5.6: icmp_seq=16 ttl=64 time=0.193 ms
64 bytes from 192.168.5.6: icmp_seq=17 ttl=64 time=369.145 ms
64 bytes from 192.168.5.6: icmp_seq=18 ttl=64 time=449.103 ms
64 bytes from 192.168.5.6: icmp_seq=19 ttl=64 time=0.192 ms
64 bytes from 192.168.5.6: icmp_seq=20 ttl=64 time=718.485 ms
64 bytes from 192.168.5.6: icmp_seq=21 ttl=64 time=0.173 ms
64 bytes from 192.168.5.6: icmp_seq=22 ttl=64 time=0.198 ms
64 bytes from 192.168.5.6: icmp_seq=23 ttl=64 time=0.179 ms
64 bytes from 192.168.5.6: icmp_seq=24 ttl=64 time=0.196 ms
64 bytes from 192.168.5.6: icmp_seq=25 ttl=64 time=0.189 ms
64 bytes from 192.168.5.6: icmp_seq=26 ttl=64 time=809.865 ms
64 bytes from 192.168.5.6: icmp_seq=27 ttl=64 time=0.158 ms
64 bytes from 192.168.5.6: icmp_seq=28 ttl=64 time=1.640 ms
64 bytes from 192.168.5.6: icmp_seq=29 ttl=64 time=0.175 ms
64 bytes from 192.168.5.6: icmp_seq=30 ttl=64 time=219.603 ms
64 bytes from 192.168.5.6: icmp_seq=31 ttl=64 time=990.000 ms
64 bytes from 192.168.5.6: icmp_seq=32 ttl=64 time=0.299 ms
64 bytes from 192.168.5.6: icmp_seq=33 ttl=64 time=289.938 ms
^C
--- 192.168.5.6 ping statistics ---
34 packets transmitted, 34 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.158/197.040/990.000/317.248 ms

>How-To-Repeat:
Configure a sis(4)-Interface to use manual media selection:

# ifconfig sis0 media 100baseTX mediaopt full-duplex

Then do a TCP transfer using fetch(1) or something similar.

>Fix:
Use media autoselection:

# ifconfig sis0 media autoselect

>Release-Note:
>Audit-Trail:
>Unformatted: