Date: Fri, 3 Mar 2000 16:50:52 +0100 From: =?iso-8859-1?Q?R=E9mi_Guyomarch?= <rguyom@mail.dotcom.fr> To: freebsd-net@freebsd.org Subject: TCP performance problems, Linux faster than FreeBSD ? Message-ID: <20000303165052.C23732@pingoo.ifn.fr>
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Hi,
I have a problem with FreeBSD 3.4-STABLE. When I'm downloading from some
sites I see a large number of duplicate packets comming in. If I download the
same file(s) with a Linux 2.2.14 box, I don't see those duplicate packets.
Well, a lot less I mean.
I tried to move our Squid proxy from the (too old) Linux box to the FreeBSD
one, but after some time I noticed the not so great performance and the large
number of duplicate acks, packets and bytes with 'netstat -p tcp'.
For example, I download something from msvaus.www.conxion.com using FreeBSD
and Linux. Here's the breakdown of packets I'm receiving :
(cut'n paste from a 'tcptrace' output)
FreeBSD Linux
total packets: 375 304
ack pkts sent: 375 304
pure acks sent: 1 1
unique bytes sent: 409507 409507
actual data pkts: 373 302
actual data bytes: 515333 428792
rexmt data pkts: 76 (!!) 15 <<----
rexmt data bytes: 105826 (!!) 19285 <<----
outoforder pkts: 19 11
pushed data pkts: 9 7
SYN/FIN pkts sent: 1/1 1/1
req 1323 ws/ts: N/N N/N
adv wind scale: 0 0
mss requested: 1460 bytes 1460 bytes
max segm size: 1460 bytes 1460 bytes
min segm size: 67 bytes 92 bytes
avg segm size: 1381 bytes 1419 bytes
max win adv: 8760 bytes 8760 bytes
min win adv: 8619 bytes 8619 bytes
zero win adv: 0 times 0 times
avg win adv: 8619 bytes 8619 bytes
initial window: 1460 bytes 1460 bytes
initial window: 1 pkts 1 pkts
The 'rexmt' lines are the number of duplicate packets & bytes conxion.com
is sending to my boxes. Why am I receiving 25% duplicate bytes on my fbsd
box and only 5% with Linux ??
I tried to play a bit with sysctl variables, but without much success (see
below).
I'm on a 64K leased line and I have a ~190ms (ICMP) RTT to
msvaus.www.conxion.com.
The easy answer is "conxion.com is broken", but even if they are, why Linux
doesn't seems affected ?
Here's my setup :
---------------
FreeBSD 3.4-STABLE (last cvsup & buildworld : Feb 17)
de0: <Digital 21140A Fast Ethernet> rev 0x20 int a irq 10 on pci0.14.0
de0: ACCTON EN1207 21140A [10-100Mb/s] pass 2.0
de0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet x.x.x.x netmask 0xffffff00 broadcast x.x.x.x
ether 00:00:e8:2b:bc:64
media: autoselect (100baseTX) status: active
supported media: autoselect 100baseTX <full-duplex> 100baseTX 10baseT/UTP <full-duplex> 10baseT/UTP
tun0: flags=8010<POINTOPOINT,MULTICAST> mtu 1500
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet 127.0.0.1 netmask 0xff000000
The Linux box is an old SparcStation 10 running 2.2.14 and the network
card is a "SUNW,hme" (BigMac) 100baseTX card.
root@diabolo ~ sysctl net.inet.tcp
net.inet.tcp.rfc1323: 1 (was 0)
net.inet.tcp.rfc1644: 0
net.inet.tcp.mssdflt: 512
net.inet.tcp.rttdflt: 3
net.inet.tcp.keepidle: 14400
net.inet.tcp.keepintvl: 150
net.inet.tcp.sendspace: 32768 (was 16k initially)
net.inet.tcp.recvspace: 32768 ( // )
net.inet.tcp.keepinit: 150
net.inet.tcp.log_in_vain: 0
net.inet.tcp.delayed_ack: 1
net.inet.tcp.pcbcount: 6
net.inet.tcp.always_keepalive: 1
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