Re: Using the -xen kernel rather than -xen0/U was [Xen-users] Poor hard disk performance on xen-3/dom0

[Tim Freeman <tfreeman@xxxxxxxxxxx>]

On Fri, 30 Dec 2005 12:33:46 -0800
David H <davidh.davidh@xxxxxxxxx> wrote:

> >users really should be using the -xen kernel rather than -xen0/U.
> 
> This is very good advice, and easy to follow.  If you are building Xen
> for testing or production use the "xen" kenel.  It is much more like
> the kenel in most distributions, everything compiled as a module.
> 
> Just edit the top level Makefile so that this line:
> 
> KERNELS ?= linux-2.6-xen0 linux-2.6-xenU
> 
> looks like this
> 
> KERNELS ?= linux-2.6-xen
> 
> You will get a single kernel and modules which can be used for both
> Domain0 and all DomainUs.

But in typical deployments the domU's typically have the priviliged kernel
option and backend driver options disabled.  Sounds like this is good only for
dom0, but you could get the same benefits by cd'ing to dom0's source tree and
running "ARCH=xen make menuconfig" (enabling stuff as native instead of modules
as you please). 

Or before building anything, copy over:

linux-2.6-xen-sparse/arch/xen/configs/xen_defconfig_x86_32
to
linux-2.6-xen-sparse/arch/xen/configs/xen0_defconfig_x86_32

would be easiest (but that still needs initrd for the dom0 kernel).  That at
least still maintains the slim and unpriviliged domU. 

Tim 


> 
> Copy the modules directory  /lib/modules/2.6.whatever-xen to the
> /lib/modules directory of your VM and make an initrd with mkinitrd. 
> You will need to add the initrd to your grub config.
> 
> Takes a little longer to build the kernel this way, but for most
> people it is much easier to deal with.
> 
> If this is not documented it should be.  I will take a look at the
> wiki over the weekend and add something if it is not already there.
> 
> David
> 
> 
> 
> On 12/30/05, Eric S. Johansson <esj@xxxxxxxxxx> wrote:
> > Ian Pratt wrote:
> > > I know everyone always ignores me whenever I say this, but users really
> > > should be using the -xen kernel rather than -xen0/U. The latter two are
> > > just to make build times quicker for developers. The -xen kernel has way
> > > more drivers, though built as modules, so you'll need to make an initrd.
> >
> >
> > http://www.cl.cam.ac.uk/Research/SRG/netos/xen/readmes/user/user.html#SECTION02140000000000000000
> >
> > section 2.4.2 building from source
> > ---
> >
> > unless I'm missing something, the official docs say nothing about a -xen
> > kernel (and modules).  what are more appropriate instructions for building?
> >
> > --- eric
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
> >
> 
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