[Xen-devel] UEK2 as a Xen dom0 (was: [Xen-users] Transcendent Memory ("tmem") -capable kernel now publicly released)

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> From: Joseph Glanville [mailto:joseph.glanville@xxxxxxxxxxxxxx]
> Subject: Re: [Xen-devel] [Xen-users] Transcendent Memory ("tmem") -capable 
> kernel now publicly
> released
> 
> On 23 March 2012 04:22, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> wrote:
> > Transcendent Memory ("tmem") [1] is a new approach to optimizing RAM 
> > utilization
> > in a virtualized (and, in some cases, a physical) environment
> >
> > Support for tmem has been in the Xen hypervisor since the 4.0 release, but
> > the tmem protocols require cooperation between the hypervisor and guest
> > OS kernel.  While the guest-side kernel changes are relatively simple
> > and non-intrusive, getting any new technology into any operating system
> > can be, shall we say, challenging... :-)  BUT...
> >
> > Last week, Oracle released "Oracle Unbreakable Enterprise Kernel Release 2",
> > the first publicly-available fully-supported[2] Linux kernel implementing 
> > all
> > Xen-guest-side capabilities for tmem, including "cleancache" (ephemeral tmem
> > pools), "frontswap" (persistent tmem pools), and in-kernel support for
> > "self-ballooning".
> >
> > So now, finally, it should be easy to give tmem a try!
> >
> > Brief How-To:
> 
> Hi Dan.
> 
> Is UEK2 configured with dom0 support by default or does one have to
> download the sources and recompile with appropriate options?
> 
> Joseph.

Hi Joseph --

Since UEK2 is based on Linux 3.0, I think it has all the support
necessary to be used as a dom0.  However I don't think all the
latest post-3.0 bug fixes and performance fixes for dom0 support have
been back-ported (yet).  Let me check and get back to you (or
see if another UEK2 expert will reply on-list).

In any case, the brief tmem how-to should probably have stated that
the tmem feature is primarily for use in the hypervisor and guests,
NOT dom0.  Turning it on in dom0 may have some value for Xen
systems that primarily use "file:" for disk access (i.e. are
trading off potential data loss on a system crash for higher
performance), but we don't really test that configuration.

Dan

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