Hi,
In a setup where OpenVSwitch is used with GRE tunels on top of an interface
provided by tinc, I'm experiencing significant performance degradation
problems (from 100Mb/s down to 1Mb/s in the worst case) and I'm not sure how
to fix this. The manifestation of the problem is, from the user point of view,
iperf reports ~100Mb/s and rsync reports ~1Mb/s:
$ iperf -c 91.224.149.132
------------------------------------------------------------
Client connecting to 91.224.149.132, TCP port 5001
TCP window size: 23.5 KByte (default)
------------------------------------------------------------
[ 3] local 10.0.2.27 port 57143 connected with 91.224.149.132 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 99.4 MBytes 83.3 Mbits/sec
$ rsync --progress root at
91.224.149.132:precise-server-cloudimg-amd64-disk1.img .
precise-server-cloudimg-amd64-disk1.img
32112640 12% 83.44kB/s 0:45:34
A tcpdump of iperf ( http://dachary.org/loic/good.cap ) shows no retransmission
while a tcpdump of rsync ( http://dachary.org/loic/bad.cap ) shows a frequent
"TCP Dup ACK", "TCP Retransmission", "TCP
Out-Of-Order".
I'm not sure why this happens, any hint would be greatly appreciated :-)
Cheers
--
Lo?c Dachary, Artisan Logiciel Libre
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It turns out that uploading with rsync works as fast as expected. The problem therefore seems to be : uploading works at 100Mb/s and downloading is degraded to 1Mb/s. Note that I checked that downloading on the same host without involving GRE or tinc indeed delivers 100Mb/s. This is puzzling :-) On 29/04/2014 16:31, Loic Dachary wrote:> Hi, > > In a setup where OpenVSwitch is used with GRE tunels on top of an interface provided by tinc, I'm experiencing significant performance degradation problems (from 100Mb/s down to 1Mb/s in the worst case) and I'm not sure how to fix this. The manifestation of the problem is, from the user point of view, iperf reports ~100Mb/s and rsync reports ~1Mb/s: > > $ iperf -c 91.224.149.132 > ------------------------------------------------------------ > Client connecting to 91.224.149.132, TCP port 5001 > TCP window size: 23.5 KByte (default) > ------------------------------------------------------------ > [ 3] local 10.0.2.27 port 57143 connected with 91.224.149.132 port 5001 > [ ID] Interval Transfer Bandwidth > [ 3] 0.0-10.0 sec 99.4 MBytes 83.3 Mbits/sec > > > $ rsync --progress root at 91.224.149.132:precise-server-cloudimg-amd64-disk1.img . > precise-server-cloudimg-amd64-disk1.img > 32112640 12% 83.44kB/s 0:45:34 > > A tcpdump of iperf ( http://dachary.org/loic/good.cap ) shows no retransmission while a tcpdump of rsync ( http://dachary.org/loic/bad.cap ) shows a frequent "TCP Dup ACK", "TCP Retransmission", "TCP Out-Of-Order". > > I'm not sure why this happens, any hint would be greatly appreciated :-) > > Cheers >-- Lo?c Dachary, Artisan Logiciel Libre -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 263 bytes Desc: OpenPGP digital signature URL: <http://www.tinc-vpn.org/pipermail/tinc/attachments/20140429/a7aad2f0/attachment.sig>
On Tue, Apr 29, 2014 at 04:31:26PM +0200, Loic Dachary wrote:> In a setup where OpenVSwitch is used with GRE tunels on top of an interface > provided by tinc, I'm experiencing significant performance degradation > problems (from 100Mb/s down to 1Mb/s in the worst case) and I'm not sure how > to fix this. The manifestation of the problem is, from the user point of > view, iperf reports ~100Mb/s and rsync reports ~1Mb/s:A likely problem is that the GRE tunnel sends packets larger than the PMTU without the DF bit set, which causes tinc to fragment those packets, which reduces the effective bandwidth and increases the chance that packets are dropped. Try setting the MTU of the GRE interface manually to 1400 or even 1300, and see if that makes a difference. -- Met vriendelijke groet / with kind regards, Guus Sliepen <guus at tinc-vpn.org> -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://www.tinc-vpn.org/pipermail/tinc/attachments/20140429/4cd40a33/attachment.sig>