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Fasiha Ashraf

2009-Nov-12 12:59 UTC

[Xen-users] strange ethtool output in xen environment

I want to check the speed like features of my Ethernet in dom0 and domUs. But in
virtualized environment it gives strange output why is that so? how to check it
otherwise?
Non-virtualized FC11
[root@fasiha home]# ethtool eth0
Settings for eth0:
    Supported ports: [ TP ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Supports auto-negotiation: Yes
    Advertised link modes:  10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Advertised auto-negotiation: Yes
    Speed: 100Mb/s
    Duplex: Full
    Port: Twisted Pair
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: g
    Wake-on: g
    Current message level: 0x000000ff (255)
    Link detected: yes

Xen Dom0
[root@Server1-FC11 ~]# ethtool eth0
Settings for eth0:
    Link detected: yes
[root@Server1-FC11 ~]# mii-tool eth0
SIOCGMIIPHY on ''eth0'' failed: Operation not supported

Xen DomU
[root@F11-G1S1 /]# ethtool eth0
Settings for eth0:
    Link detected: yes

Regards
Fasiha Ashraf


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Satish Chowdhury

2009-Nov-13 06:27 UTC

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Re: [Xen-devel] strange ethtool output in xen environment

On Thu, Nov 12, 2009 at 6:29 PM, Fasiha Ashraf <feehapk@yahoo.co.in>
wrote:
>  I want to check the speed like features of my Ethernet in dom0 and domUs.
> But in virtualized environment it gives strange output why is that so? how
> to check it otherwise?
> Non-virtualized FC11
> [root@fasiha home]# ethtool eth0
> Settings for eth0:
>     Supported ports: [ TP ]
>     Supported link modes:   10baseT/Half 10baseT/Full
>                             100baseT/Half 100baseT/Full
>                             1000baseT/Half 1000baseT/Full
>     Supports auto-negotiation: Yes
>     Advertised link modes:  10baseT/Half 10baseT/Full
>                             100baseT/Half 100baseT/Full
>                             1000baseT/Half 1000baseT/Full
>     Advertised auto-negotiation: Yes
>     Speed: 100Mb/s
>     Duplex: Full
>     Port: Twisted Pair
>     PHYAD: 1
>     Transceiver: internal
>     Auto-negotiation: on
>     Supports Wake-on: g
>     Wake-on: g
>     Current message level: 0x000000ff (255)
>     Link detected: yes
>
> Xen Dom0
> [root@Server1-FC11 ~]# ethtool eth0
> Settings for eth0:
>     Link detected: yes
>
eth0 is bridge interface.  peth0 is the physical interface.

[root@Server1-FC11 ~]# mii-tool eth0> SIOCGMIIPHY on ''eth0'' failed: Operation not supported
>
> Xen DomU
> [root@F11-G1S1 /]# ethtool eth0
> Settings for eth0:
>     Link detected: yes
>You are using para-VM, use HVM to see a emulated  device and the link speed.
>
> Regards
> Fasiha Ashraf
> ------------------------------
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> http://lists.xensource.com/xen-devel
>
>

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Fasiha Ashraf

2009-Nov-13 08:44 UTC

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[Xen-users] Re: [Xen-devel] strange ethtool output in xen environment

Ok thanks. In case of paravirt guests, are they using the same link(interface)
as my dom0?

Regards,
Fasiha Ashraf

--- On Fri, 13/11/09, Satish Chowdhury
<satish.chowdhury@oneconvergence.com> wrote:

From: Satish Chowdhury <satish.chowdhury@oneconvergence.com>
Subject: Re: [Xen-devel] strange ethtool output in xen environment
To: "Fasiha Ashraf" <feehapk@yahoo.co.in>
Cc: "xen" <xen-devel@lists.xensource.com>,
xen-users@lists.xensource.com
Date: Friday, 13 November, 2009, 11:27 AM



On Thu, Nov 12, 2009 at 6:29 PM, Fasiha Ashraf <feehapk@yahoo.co.in>
wrote:




I want to check the speed like features of my Ethernet in dom0 and domUs. But in
virtualized environment it gives strange output why is that so? how to check it
otherwise?
Non-virtualized FC11


[root@fasiha home]# ethtool eth0
Settings for eth0:
    Supported ports: [ TP ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 


    Supports auto-negotiation:
 Yes
    Advertised link modes:  10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Advertised auto-negotiation: Yes


    Speed: 100Mb/s
    Duplex: Full
    Port: Twisted Pair
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: g
    Wake-on: g
    Current message level: 0x000000ff (255)


    Link detected: yes

Xen Dom0
[root@Server1-FC11 ~]# ethtool eth0
Settings for eth0:
    Link detected: yes


eth0 is bridge interface.  peth0 is the physical interface.



[root@Server1-FC11 ~]# mii-tool eth0


SIOCGMIIPHY on ''eth0'' failed: Operation not supported

Xen DomU
[root@F11-G1S1 /]# ethtool eth0
Settings for eth0:
    Link detected: yes


You are using para-VM, use HVM to see a emulated  device and the link speed.




Regards
Fasiha Ashraf




       
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John Haxby

2009-Nov-13 11:01 UTC

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Re: [Xen-users] strange ethtool output in xen environment

On 12/11/09 12:59, Fasiha Ashraf wrote:> I want to check the speed like features of my Ethernet in dom0 and 
> domUs. But in virtualized environment it gives strange output why is 
> that so? how to check it otherwise?
> Non-virtualized FC11
> [root@fasiha home]# ethtool eth0
>
The question makes no sense, really.   The speed of a NIC is dependent 
on physical characteristics: the speed at which it can generate and 
observe a signal.   A virtual NIC doesn''t have those physical 
characteristics and the emulated NIC in a domU doesn''t know what 
physical hardware is going to actually send or receive signals.  A 
virtual NIC can report a speed, but if it does, it''s just lying so that
it can give some plausible answer.

In dom0 you do have access to the physical NIC: it might be eth0 but it 
might be something else.   On different machines, "eth0" might be 
different things depending on how the bridge is set up.  On a reasonably 
"standard" xen 3.4.0 eth0 is a bridge and the NIC is peth0 (you can
see
that from brctl show).   Bridges don''t correspond to NICs so
"ethtool
eth0" is relatively useless.

In domU you have a virtual NIC and since ethtool is reporting physical 
characteristics, anything you might or might not see is made up by the 
driver.

jch

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