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

[Matthieu Patou <mat+Informatique.xen@xxxxxxxxx>]

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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