Re: [Xen-users] Network performance with HVM DomU

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, May 26, 2016 at 06:08:53PM +0200, Christoph wrote:
> > Since I've been dealing with netfront issues recently also (not on Linux
> > or
> > Windows), I would recommend that you take a capture of the packets seen
> > in
> > the bridge using tcpdump and analize it with Wireshark or something
> > similar. FWIW, I use the following rune in order to make tcpdump
> > generate a
> > file that I can open with Wireshark (this is all on Dom0):
> > 
> > # brctl show
> > (then you will have to identify a vif that belongs to one of the DomUs
> > involved in the transaction, they have the format vif<domid>.<order>).
> > # tcpdump -n -i <if> -s0 -w <output>.pcap
> > 
> > Then you can open the resulting <output>.pcap and check for
> > retransmissions,
> > or anything strange.
> > 
> > Roger.
> 
> I have seen on the dom0 host there are 2 net ifaces for the hvm windows domU
> (marax):
> 
> 40: vif10.0-emu: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
> master xenbr5 state UNKNOWN qlen 500
>     link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
>     inet6 fe80::fcff:ffff:feff:ffff/64 scope link
>        valid_lft forever preferred_lft forever
> 41: vif10.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master
> xenbr5 state UP qlen 32
>     link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
> 
> xl network-list marax
> Idx BE Mac Addr.         handle state evt-ch   tx-/rx-ring-ref BE-path
> 0   0  00:16:3e:05:01:10     0     4     16 16269/16268
> /local/domain/0/backend/vif/10/0
> 
> it is normal? all my other domU's are linux domU's (pv) they have each only
> 1 net iface on dom0...

Yes, for HVM domains you will always see two network interfaces on Dom0 (or 
the driver domain). One is the tap interface, used by the network card 
emulated by QEMU, while the other one is the network interface created by 
netback.

Roger.

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