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Message-ID: <20091130213727.2f4047d2@houba> Date: Mon, 30 Nov 2009 21:37:27 +0100 From: Frederic Leroy <fredo@...rox.org> To: "Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> Cc: Netdev <netdev@...r.kernel.org>, Asdo <asdo@...ftmail.org> Subject: Re: scp stalls mysteriously Le Mon, 30 Nov 2009 22:18:22 +0200 (EET), "Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> a écrit : > On Mon, 30 Nov 2009, Frederic Leroy wrote: > > Thanks, at least ....3.... shows that cwnd (congestion window, the > 2nd to last field in /proc/net/tcp) goes to zero which it never ever > should. ...I'll start reading some code to figure out the cause for > that. > > How much is your RTT btw? The RTT is ~ 1.4ms. The following trace has a rtt as big as 5ms but most of the time, it's under 1.4ms and periodically grow to 3ms. ------------------------------------------- 64 bytes from sg (192.168.1.19): icmp_seq=681 ttl=64 time=1.26 ms 64 bytes from sg (192.168.1.19): icmp_seq=682 ttl=64 time=1.26 ms 64 bytes from sg (192.168.1.19): icmp_seq=683 ttl=64 time=1.34 ms 64 bytes from sg (192.168.1.19): icmp_seq=684 ttl=64 time=2.01 ms 64 bytes from sg (192.168.1.19): icmp_seq=686 ttl=64 time=2.15 ms 64 bytes from sg (192.168.1.19): icmp_seq=687 ttl=64 time=5.07 ms 64 bytes from sg (192.168.1.19): icmp_seq=688 ttl=64 time=1.19 ms 64 bytes from sg (192.168.1.19): icmp_seq=689 ttl=64 time=1.30 ms 64 bytes from sg (192.168.1.19): icmp_seq=690 ttl=64 time=1.19 ms 64 bytes from sg (192.168.1.19): icmp_seq=691 ttl=64 time=1.14 ms ------------------------------------------- > The RTO timeout easily goes up to 120 > secods similar to what I found myself already. Thus I'm not sure if > this stall would be "infinite" after all. I notice that grep '":0016" /proc/net/tcp' stop to report something when it stalls. Is the connection closed ? > I've some problem in .3. case in matching timing of the proc/net/tcp > dump and the tcpdump ... did you perhaps cut it somewhere? No, I didn't cut it. > This might > point out to yet another problem, however, I'm not sure what I can > atm trust in the logs. ...Timestamps would probably help me a bit > (I've changed also sleep to do 0.01 granularity): > > while [ : ]; do date "+%s.%N"; grep ":0016" /proc/net/tcp; sleep > 0.01; done | tee scp_stall-houba.x.proc_net_tcp > (Please run start while loop before starting the transfer and all the > way until the connection is already killed and only then stop the > loop). I took care to timings this time. I did as you said. > What happened in .2. case I've very little idea, proc/net/tcp does > claim retransmission would have happened on TCP layer but that never > went into tcpdump log (the kind of thing might have happened in > the .3. case too which is why I asked for the timestamps for matching > captures more exactly but there were some retransmissions earlier in > the log so I cannot be sure). Can you also check that tcpdump doesn't > lose any packets, it should show: "0 packets dropped by kernel" when > you ctrl-c it. I still have the logs, O packet dropped : ------------------------------------------- houba tmp # tcpdump -i wlan1 -s 1500 -w /tmp/ssh_stall-houba.1.pcap -vv ether host 00:40:45:09:3f:3f tcpdump: listening on wlan1, link-type EN10MB (Ethernet), capture size 1500 bytes ^C8923 packets captured 8923 packets received by filter 0 packets dropped by kernel houba tmp # tcpdump -i wlan1 -s 1500 -w /tmp/scp_stall-houba.3.pcap -vv ether host 00:40:45:09:3f:3f tcpdump: listening on wlan1, link-type EN10MB (Ethernet), capture size 1500 bytes ^C17045 packets captured 17045 packets received by filter 0 packets dropped by kernel houba tmp # ------------------------------------------- -- Frédéric Leroy -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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