Xen users - Feb 2009 - Does Xen 3.3 support giga bit network in the guest?

Does Xen3.3 support gigabit network at the guest?
I know in Xen3.0, which comes with FC8, supports at most 100Mbps
in guest if setup is fully virtualized.


Abdul Qadeer


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Abdul Qadeer wrote:
> Does Xen3.3 support gigabit network at the guest?
> I know in Xen3.0, which comes with FC8, supports at most 100Mbps
> in guest if setup is fully virtualized.
The virtual NIC doesn''t limit its speed to 100Mb.   It reports that to 
the guest OS because it has to report _something_ but it doesn''t 
throttle back to 100Mb.    The only way to find out the actual transfer 
speed is to measure it -- what you actually get depends on a variety of 
factors, but not the emulated link speed.

jch

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Dear,

The Guest HVM (fully virt) emulate drivers for NIC''s of qemu the
options
are:
ne2k_isa, ne2k_pci, rtl8139, and  smc91c111.

Model: Specified using model=variable, where variable is one of the specific
types of network
cards emulated by QEMU. This option is therefore only useful if you are
using ioemu as the type
of network driver you are using. Valid values are lance, ne2k_isa, ne2k_pci,
rtl8139, and
smc91c111. The default value is ne2k_pci if you are using QEMU (i.e., ioemu)
network drivers

For emulate 1Gpbs use gplpv in
http://wiki.xensource.com/xenwiki/XenWindowsGplPv/Installing

Att,
Horacio Ibrahim


On Wed, Feb 11, 2009 at 8:33 AM, John Haxby <john.haxby@oracle.com> wrote:
> Abdul Qadeer wrote:
>
>> Does Xen3.3 support gigabit network at the guest?
>> I know in Xen3.0, which comes with FC8, supports at most 100Mbps
>> in guest if setup is fully virtualized.
>>
>
> The virtual NIC doesn''t limit its speed to 100Mb.   It reports
that to the
> guest OS because it has to report _something_ but it doesn''t
throttle back
> to 100Mb.    The only way to find out the actual transfer speed is to
> measure it -- what you actually get depends on a variety of factors, but
not
> the emulated link speed.
>
> jch
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>


-- 
ITIL: "An industry accepted way of doing something, that works" (Aidan
Lawes)


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When I do the mentioned procedure and re-start the guest, all these changes
go away
automatically.  Looks like Xen "wipes them out".  I tried to set these
file
rights to read only
but since Xen properly runs from root only, it probably chmod on those files
and again wipes
out the changes.  My guess is that if Xen sees that some argument is not
valid due to some
reason (may be absence of mentioned driver or something), it rejects it and
changes it to some
default?

Were you able to persist and utilize these changed values?

Abdul Qadeer

On Wed, Feb 11, 2009 at 3:54 PM, horacio ibrahim
<horacioibrahim@gmail.com>wrote:
> Dear,
>
> The Guest HVM (fully virt) emulate drivers for NIC''s of qemu the
options
> are:
> ne2k_isa, ne2k_pci, rtl8139, and  smc91c111.
>
> Model: Specified using model=variable, where variable is one of the
> specific types of network
> cards emulated by QEMU. This option is therefore only useful if you are
> using ioemu as the type
> of network driver you are using. Valid values are lance, ne2k_isa,
> ne2k_pci, rtl8139, and
> smc91c111. The default value is ne2k_pci if you are using QEMU (i.e.,
> ioemu) network drivers
>
> For emulate 1Gpbs use gplpv in
> http://wiki.xensource.com/xenwiki/XenWindowsGplPv/Installing
>
> Att,
> Horacio Ibrahim
>
>
> On Wed, Feb 11, 2009 at 8:33 AM, John Haxby <john.haxby@oracle.com>
wrote:
>
>> Abdul Qadeer wrote:
>>
>>> Does Xen3.3 support gigabit network at the guest?
>>> I know in Xen3.0, which comes with FC8, supports at most 100Mbps
>>> in guest if setup is fully virtualized.
>>>
>>
>> The virtual NIC doesn''t limit its speed to 100Mb.   It reports
that to the
>> guest OS because it has to report _something_ but it doesn''t
throttle back
>> to 100Mb.    The only way to find out the actual transfer speed is to
>> measure it -- what you actually get depends on a variety of factors,
but not
>> the emulated link speed.
>>
>> jch
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@lists.xensource.com
>> http://lists.xensource.com/xen-users
>>
>
>
>
> --
> ITIL: "An industry accepted way of doing something, that works"
(Aidan
> Lawes)
>

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On Wed, Feb 11, 2009 at 5:33 PM, John Haxby <john.haxby@oracle.com>
wrote:
> The virtual NIC doesn''t limit its speed to 100Mb.   It reports
that to the
> guest OS because it has to report _something_ but it doesn''t
throttle back
> to 100Mb.
Have you tested it? Which HVM OS?
My test (with a rather old RHEL4 HVM) seems to indicate that when
ethtool show 100Mbps link speed on emulated Realtek NIC, that''s the
actual speed. I only get 62 Mbps with iperf.

Using pv drivers (from RHEL''s kmod-xenpv), ethtool doesn''t
report
ANYTHING in regards to speed, and iperf (on the same HVM domU) got
about 3 Gbps.

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On Wed, Feb 11, 2009 at 8:28 PM, Abdul Qadeer <qadeer.qadeer@gmail.com>
wrote:
> When I do the mentioned procedure and re-start the guest, all these changes
> go away
> automatically.  Looks like Xen "wipes them out".
That''s not right. How did you create your domUs? Using the traditional
"xm create", or with virt-install/virt-manager?

What did you modify? is it files on /etc/xen, or using virsh?


Since you want to use Xen 3.3 anyway, instead of changing the emulated
NIC type I''d suggest you try one of these :
- convert your HVM domU to PV. Easiest when running Linux domU. This
has additional benefit of giving you maximum possible speed with
regards to CPU, disk, and network.
- use PV drivers. For Windows HVM, use James Harper''s GPLPV. For Linux
HVM, you might be able to find kmod-xenpv RPM or a module called
xennet or xen-vnif
- use stubdom (only available on Xen 3.3)

Regards,

Fajar

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Forgot to cc to the group.  Sorry John to put this duplicate mail in your
inbox.

---------- Forwarded message ----------
From: Abdul Qadeer <qadeer.qadeer@gmail.com>
Date: Wed, Feb 11, 2009 at 6:24 PM
Subject: Re: [Xen-users] Does Xen 3.3 support giga bit network in the guest?
To: John Haxby <john.haxby@oracle.com>


The virtual NIC doesn''t limit its speed to 100Mb.   It reports that to
the
> guest OS because it has to report _something_ but it doesn''t
throttle back
> to 100Mb.    The only way to find out the actual transfer speed is to
> measure it -- what you actually get depends on a variety of factors, but
not
> the emulated link speed.

I see.  I tried to do a quick measurement using wget.  There were two
guests.  I placed a big fie in one guest and get it from the other guest
using wget.  The max speed was about 2.2MBps (i.e. about 16 Mbps).  That is
very poor speed indeed and the test was not able to saturate the available
bandwidth (i.e 100 Mbps as shown in guest and actually a 1000 Mbps in
dom0).  But as you said that there can be many facors (my guess is factors
like emulation and the memory subsystem and not to forget that the system is
using fully virtualized guests).

So probably I need to use para-virtualized net front drivers to get better
througput?

Thanks,
Abdul Qadeer


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On Wed, Feb 11, 2009 at 6:40 PM, Fajar A. Nugraha <fajar@fajar.net> wrote:
> On Wed, Feb 11, 2009 at 8:28 PM, Abdul Qadeer
<qadeer.qadeer@gmail.com>
> wrote:
> > When I do the mentioned procedure and re-start the guest, all these
> changes
> > go away
> > automatically.  Looks like Xen "wipes them out".
>
> That''s not right. How did you create your domUs? Using the
traditional
> "xm create", or with virt-install/virt-manager?

The host (dom0) and guests (domU) were FC8.  I was using the Xen 3.0
kernel which comes with FC8.  I created domUs using virt-manager GUI


>
>
> What did you modify? is it files on /etc/xen, or using virsh?

I manually edited the files in etc/xen.


>
> Since you want to use Xen 3.3 anyway, instead of changing the emulated
> NIC type I''d suggest you try one of these :
> - convert your HVM domU to PV. Easiest when running Linux domU. This
> has additional benefit of giving you maximum possible speed with
> regards to CPU, disk, and network.
> - use PV drivers. For Windows HVM, use James Harper''s GPLPV. For
Linux
> HVM, you might be able to find kmod-xenpv RPM or a module called
> xennet or xen-vnif
> - use stubdom (only available on Xen 3.3)


Thank you on mentioning all the alternatives.   I will go through them to
understand
them fully before asking questions on them.

I have been trying to build latest Xen code from source.  There have been
different
issues (e.g. Xen kernel not booting due to LVM problems, or initrd failing
because
it can''t find SCSI based raid etc.).

I did

make world
make install
depmod
mkinitrd ...

During compilation there was an error that it can not find compile.h in
include2.  But
since it didn''t stop on that, I assumed its not critical?

So my immediate question is that if I have to include a new driver in the
kernel code
which Xen downloads (usually 2.6.18.8), and I am going for para
virtualization, it would
not be that straight to just put the drivers in the kernel and to re-build?
So how exactly
this work is done to include new drivers in xen?

Thank you,
Abdul Qadeer


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On Wed, Feb 11, 2009 at 9:31 PM, Abdul Qadeer <qadeer.qadeer@gmail.com>
wrote:
>> That''s not right. How did you create your domUs? Using the
traditional
>> "xm create", or with virt-install/virt-manager?
>
> The host (dom0) and guests (domU) were FC8.  I was using the Xen 3.0
> kernel which comes with FC8.  I created domUs using virt-manager GUI
>
Any particular reason to use FC8?
Personally I use RHEL5.3 (Centos should be just the same). It''s easier
to get support since many people use it.

I''m not sure what Xen version FC8 has, but RHEL/CentOS has been
updated to Xen 3.1 plus lots of backports and fixes (even though RPM
version number stays 3.0)
As a side note, on RHEL/Centos5 you can easily try out Xen 3.3.1 using
Gitco''s RPM http://www.gitco.de/repo/
>
>>
>> What did you modify? is it files on /etc/xen, or using virsh?
>
> I manually edited the files in etc/xen.
>
... and you start it later using the GUI, right?
I haven''t used virt-manager much, but there''s a possibility
that the
GUI stores its own settings elsewhere, and the settings are written to
/etc/xen/* when you start the domain. In other words, you need to find
another way to edit domU config (either via GUI or virsh).
>
> I have been trying to build latest Xen code from source.  There have been
> different
> issues (e.g. Xen kernel not booting due to LVM problems, or initrd failing
> because
> it can''t find SCSI based raid etc.).
It''s a lot easier to simply :
- Use RHEL/Centos5
- install kernel-xen
- update xen and related package from Gitco.

That way all Redhat kernel stuff (including what modules are
available, what should be included on initrd, etc.) stays the same,
and (usually) you don''t have to worry about a missing module prevents
a system from booting.

Regards,

Fajar

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>
> Since you want to use Xen 3.3 anyway, instead of changing the emulated
>> NIC type I''d suggest you try one of these :
>> - convert your HVM domU to PV. Easiest when running Linux domU. This
>> has additional benefit of giving you maximum possible speed with
>> regards to CPU, disk, and network.
>> - use PV drivers. For Windows HVM, use James Harper''s GPLPV.
For Linux
>> HVM, you might be able to find kmod-xenpv RPM or a module called
>> xennet or xen-vnif
>> - use stubdom (only available on Xen 3.3)
>
>
As per your suggestions, I used suggestion 1 (i.e. of using PV based domU)
and
it worked fine and I was able to get about 900 Mbps throughput on a 1 g
card.  On
the other hand on fully virtualized thing I was getting about 40 Mbps on
average.  So
the difference was substantial.

Though I have one question.  By "PARA-VIRTUALIZATION" I understand
that, the
guest OS code is change such that the conventional assumption of OS that it
is
running in ring 0 goes away.  I used FC8 as dom0 and the same FC8 DVD worked
for domU, while selecting para-virtualized option.  So I am surprized did
Xen changed
the required Linux Kernel stuff in the guest, on the fly?  Or did FC
distribution had
the support to be used as para-virtualized guest?

Thank you,
Abdul Qadeer


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On Thu, Feb 12, 2009 at 11:50 PM, Abdul Qadeer <qadeer.qadeer@gmail.com>
wrote:
> I used FC8 as dom0 and the same FC8 DVD worked
> for domU, while selecting para-virtualized option.  So I am surprized did
> Xen changed
> the required Linux Kernel stuff in the guest, on the fly?
No.
>  Or did FC
> distribution had
> the support to be used as para-virtualized guest?
FC8 and above, RHEL/Centos5, and later updates of RHEL4 has a special
kernel-xen (or kernel-xenU) that is selected when installed as PV
guest.

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