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[Xen-users] slow network with gplpv drivers in vlan setup

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] slow network with gplpv drivers in vlan setup
From: Matthieu Patou <mat+Informatique.xen@xxxxxxxxx>
Date: Mon, 08 Feb 2010 23:55:39 +0300
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Hello James,

I faced quite a long time ago a problem on some of my servers:
network interface with gplpv driver has an horrible throughput (~6minute to copy ~15MBytes). I supposed it's partially linked to my setup as I have a vlan interface in the dom0 in the bridge (because I want to put some PV/HV servers in different vlans.

The problem occurs only with servers/workstation not on the same server host (ie. communication domU/domU on the same host are ok and dom0/domU also).

* If i put the plain interface (ie. eth0) in the bridge and do the vlan
* Without GPLPV the throughput is OK

Today I remade some test:

* I tried the 0.11.0.188
* I tried to desactivate checksum offload

As a last test I deactivated scatter/gather and it turns out that it make it.

I have two captures:
http://www.matws.net/mat/misc/xen_slow.gz
http://www.matws.net/mat/misc/xen_notslow_part.gz

Any chance for an explanation ? what scatter/gather is supposed to bring ?

Matthieu.

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