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Re: [Xen-users] Network stalls

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Subject: Re: [Xen-users] Network stalls
From: David Diaz i Torrico <ddiaz@xxxxxxxx>
Date: Mon, 21 Jun 2010 13:12:29 +0200
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After a bunch of tests and sniffings I found out that the problem was not due 
Xen, it is caused by the 2.6.3x kernels.

It looks like all kernels after 2.6.18 have issues with the congestion control 
which make stall the connections at random; Disabling the whole congestion 
control stuff, seems to have resolved the problem.

A Dimarts, 15 de Juny de 2010, David Diaz i Torrico va escriure:
> Hello,
> I recently set a new server (a HP Proliant with 2 Quad Xeon 2GHz and 8GB 
> with a Slackware 13 64Bits, where I installed Xen 4.0, with the kernel 
> (the same for dom0 and for domU), and I set up a virtual mail 
> from which several people retrieve its mail.
> When i try to download big files or retrieve big mails from that server, it 
> often start to slow down to 4-5Kb/s untill it finally stalls after some 
> of normal download (800-500Kb/s), it doesn't happen nor in the same point of 
> download, nor to the same users/computers. A user can try to download a 
> for example, 20 times without any success at all and then suddenly it starts 
> to download correctly, and it seems to rarely happen with small mails.
> I tried to deactivate the ethernet checksuming, as I've seen to solve the 
> problem in former versions, but it gives me an error getting the rx value:
> # ethtool -k eth0
> Offload parameters for eth0:
> Cannot get device rx csum settings: Operation not supported
> rx-checksumming: off
> tx-checksumming: off
> By the way, my dmesg has a bunch of these errors:
> "Attempting to checksum a non-TCP/UDP packet, dropping a protocol 1 packet"
> I'm not sure if this is also a related problem or not.
> Now I don't have any clue about what or where to look, so, any ideas?
> _______________________________________________
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