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RE: [Xen-devel] RE: [Xen-users] How to: Improve Network Throughput of a

To: <bderzhavets@xxxxxxxxx>
Subject: RE: [Xen-devel] RE: [Xen-users] How to: Improve Network Throughput of a XEN kernel?
From: Mike Viau <viaum@xxxxxxxxxxxxxxx>
Date: Mon, 1 Mar 2010 14:52:00 -0500
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
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Why using grub2 vs grub is baffling am not sure....

I think I'd prefer to use the kernel command line in grub2 so that the options may be changed easier laster on. However I still have been having so success with boot XEN with Ubuntu's grub2 boot loader.

Am I correct to conclude CONFIG_CMDLINE_BOL must = N to allow GRUB2 to pass kernel options?

I have read through the Wiki page at http://wiki.xensource.com/xenwiki/XenCommonProblems. I am running a 64-bit Xen Hypervisor.

Thus far I have been having no success with using the example entry found at http://old.nabble.com/Strange-interaction-from-grub2-and-XEN-td26464067.html

A question regarding that entry is what would be the root device when there are separate /boot and root partitions? I am using the partition with the /boot (grub2) as my 'set root' device right?

I am also using the dummy=dummy as the first option on the first module line, again as discovered on the wiki.

Additionally posted on another thread here in the Xen mailing list was:
> On 1 March 2010 08:09, Luke Carrier <luke.carrier@xxxxxxxxx> wrote:
>> Not sure about Debian, but I know Ubuntu isn’t ideal for Xen any more
>> because of the presence of GRUB2 – the new boot loader doesn’t support
>> passing certain command lines and the current multiboot implementation
>> breaks the method Xen uses to load the Dom0 kernel – you can’t use Ubuntu
>> 9.10 Server with Xen.

I am confused now because Boris clearly created a wordpress.com weblog in where Ubuntu 9.10 Server was
used with XEN.

Lastly, out of curiosity, what (or what kind) of commands cannot be passed with GRUB2?


Date: Sat, 27 Feb 2010 11:20:31 -0800
From: bderzhavets@xxxxxxxxx
Subject: Re: [Xen-devel] RE: [Xen-users] How to: Improve Network Throughput of a XEN kernel?
To: mike.viau@xxxxxxxxxxxxxxx
CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx

In Xen Wiki is mentioned , that parameters for kernel may be set via command line as follows:-
module (hd1,10)/vmlinuz-  dummy=dummy  root=/dev/sda7 ro console=tty0
# cat /proc/cmdline

shows that GRUB2 skips first argument, what causes problem.

Compiling built-in CMD_LINE is just an option.
Read all Wiki written by Pasi and  you would never be surprised ;)

> P.S: What is your feeling on using a recent Ubuntu system with
> grub-legacy as the boot loader? I noticed that Squeeze has adopted grub2 > package as well too...

I have development Xen 3.4.3 instance on top Ubuntu 9.10 Server with GRUB2 ( baremetall) loading any from 3 mentioned bellow kernels under Xen 3.4.3

3.) xenified

with no problems with dummy=dummy as first parameter ( thanks Pasi).
It may also may be done via compiling kernels with built-in CMD_LINE.
It works fine as well.


--- On Sat, 2/27/10, Mike Viau <viaum@xxxxxxxxxxxxxxx> wrote:

From: Mike Viau <viaum@xxxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: [Xen-users] How to: Improve Network Throughput of a XEN kernel?
To: bderzhavets@xxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
Date: Saturday, February 27, 2010, 12:03 PM

Yes, thank you Boris for pointing that out. I found that was defiantly true. The 3.2.1 xen hypervisor could only boot the 2.6.26-2 xen kernel and the xenified

Additionally I found that:

Xend does not start when using pv_ops dom0 kernel?

In December 2009 pv_ops dom0 kernel modules were renamed to have a "xen-" prefix in them, ie. "evtchn.ko" became "xen-evtchn.ko".

This makes Xen 3.4.x xend fail to start, because it tried to load "evtchn.ko", but that doesn't exist. You need to load "xen-evtchn.ko" and then start xend. Fedora 12 xen-3.4.2-2 rpms have this problem fixed.

Also make sure you have xenfs mounted to "/proc/xen", that's needed aswell.

[Source: http://wiki.xensource.com/xenwiki/XenParavirtOps]

And it appears the Debian xen-3.4.2-2 debs (in squeeze) have not fixed this problem.

Lastly I am still doing some reading on the grub2 package and how to configure it. It turns out that I have been using grub-legacy (or just good old grub) for so long that configuring the grub2 boot loader is turning out to be my own personal kryptonite.


I am still working on getting the hypervisor to load the dom0 kernel in a Ubuntu system.


I have noticed an example in your wordpress @ Set up Xen 3.4.3-rc2 & Libvirt 0.7.0 Dom0 (with xenified aka Suse kernel) on top of Ubuntu 9.10 Server


With CONFIG_CMDLINE="root=/dev/sdb11 ro console=tty0"


menuentry "Xen 3.4 / Ubuntu 9.10 kernel xenified" {
insmod ext2
set root=(hd1,10)
multiboot (hd1,10)/xen-3.4.gz
module (hd1,10)/vmlinuz-
module (hd1,10)/initrd-


I am sure you wouldn't of mentioned the CONFIG_CMDLINE kernel option is it was not important for using with grub2 right? I have not have to compile a kernel with the command line previous as I was just able to supply the arguments on the kernel line of my menu.lst (grub configuration file).

P.S: What is your feeling on using a recent Ubuntu system with grub-legacy as the boot loader? I noticed that Squeeze has adopted grub2 package as well too...


Date: Sat, 27 Feb 2010 04:32:59 -0800
From: bderzhavets@xxxxxxxxx
Subject: Re: FW: [Xen-users] How to: Improve Network Throughput of a XEN kernel?
To: jbeulich@xxxxxxxxxx; mike.viau@xxxxxxxxxxxxxxx
CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx

You cannot load pvops kernel under xen-hypervisor 3.2.1  ( >=3.4.0 in general)


--- On Fri, 2/26/10, Mike Viau <viaum@xxxxxxxxxxxxxxx> wrote:

From: Mike Viau <viaum@xxxxxxxxxxxxxxx>
Subject: FW: [Xen-users] How to: Improve Network Throughput of a XEN kernel?
To: bderzhavets@xxxxxxxxx, jbeulich@xxxxxxxxxx
Cc: xen-users@xxxxxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx
Date: Friday, February 26, 2010, 3:19 PM

Hello again,

Just a quick update...

I was really hoping it was just going to be an issue with the kernel .config, however I copied exact configuration from the working Debain 2.6.26-2-xen-amd64 kernel and used a make oldconfig but the end result was the same.

After booting the xenified ( or pvops kernel ( via both xen-hypervisor 3.2.1 or xen-hypervisor 3.4.2 the maximum data transfer to/from the Dom0 (Xen host) is ~1MB/s.

Next I plan on re-trying my efforts on a Ubuntu system to see if same network bottlenecking is present.

Date: Fri, 26 Feb 2010 09:16:59 -0800
From: bderzhavets@xxxxxxxxx
Subject: Re: [Xen-users] How to: Improve Network Throughput of a XEN kernel?
To: xen-users@xxxxxxxxxxxxxxxxxxx; viaum@xxxxxxxxxxxxxxx

Would escalate to xen-devel. (12) aka Suse xenified  was Jan Beulich stuff.
He might have an answer.

--- On Fri, 2/26/10, Mike Viau <viaum@xxxxxxxxxxxxxxx> wrote:

From: Mike Viau <viaum@xxxxxxxxxxxxxxx>
Subject: [Xen-users] How to: Improve Network Throughput of a XEN kernel?
To: xen-users@xxxxxxxxxxxxxxxxxxx
Cc: waldi@xxxxxxxxxx
Date: Friday, February 26, 2010, 12:09 PM

Hi there,

I am starting a new thread to try and solve a problem I am having will slow network throughput to the XEN host (not to a domU).

I have confirmed my problem occurs with PVOPS 'xen/master' kernel as well using http://pasik.reaktio.net/xen/pv_ops-dom0-debug/config- as the .config.

It also occurs with a forward ported xenified kernel ( using the attached config-11-xen (.config).

However when using the xen kernel found in debain lenny (2.6.26-2) for the amd64 architecture I get similiar transfer rates to my Xen host as I do on a baremetel kernel.

Bastian Blank perhaps you could point me in the right direction in regards to a debian specific customization or patch I should be aware of?

Maxium transfer rate (to/from hard disk) using the PVOPS 'xen/master' kernel and forward ported xenified kernel ( is bottlenecking at ~1MB/s. On the debain lenny xen kernel I am getting ~4.5MB/s.

I was hoping one could suggest options in the .config that might be modified in order to improve network throughput of a XEN kernel and therefor increase the data transfer rates over the netowork to and from the Xen host.

Thanks alot for any help! As always I will be willing to accept any suggestions :)


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