ANNOUNCE: Xen Transcendent Memory support now in stock Ubuntu and Fedora guest kernels

ANNOUNCE: Xen Transcendent Memory support now in stock Ubuntu and Fedora guest kernels

[Dan Magenheimer]

FYI, it has come to my attention that both the kernel in the
recently-released Ubuntu 12.10 (aka Quantal Quetzal) and the
kernel in Fedora 17 (after yum-update to a 3.5-or-later kernel)
are fully configured to support Transcendent Memory ("tmem").
Oracle's "UEK2" kernel has also had tmem support since its release
in early 2012.

To enable tmem support in Xen, it is necessary to specify
a Xen boot parameter ("tmem").  Specifying "dom0_mem="
and disabling dom0 autoballooning in the toolstack is also
highly recommended.  Then tmem must be explicitly enabled in
any tmem-capable guest kernel by specifying a boot parameter
(also "tmem") in each guest grub.conf.  Note that use of
tmem in dom0 is not recommended, so "tmem" should not be
provided as a dom0 boot parameter.

I'll try to write up a more complete current HOW-TO soon
since much of the Xen tmem documentation floating around
the web is a bit outdated.

Note that some security issues were reported in the
Xen hypervisor tmem implementation last summer.  Please
ensure your hypervisor is updated to patch XSA-15 before
enabling tmem on a Xen machine exposed to the internet!

Thanks,
Dan

P.S. If you build your own Linux guest kernels, a 3.5-or-later
kernel is required built with the following config variables:

CONFIG_FRONTSWAP=y
CONFIG_CLEANCACHE=y
CONFIG_XEN_TMEM=y
CONFIG_XEN_SELFBALLOONING=y

Re: ANNOUNCE: Xen Transcendent Memory support now in stock Ubuntu and Fedora guest kernels

[Konrad Rzeszutek Wilk]

On Tue, Nov 27, 2012 at 01:24:33PM -0800, Dan Magenheimer wrote:
> FYI, it has come to my attention that both the kernel in the
> recently-released Ubuntu 12.10 (aka Quantal Quetzal) and the
> kernel in Fedora 17 (after yum-update to a 3.5-or-later kernel)
> are fully configured to support Transcendent Memory ("tmem").

Woohoo!
> Oracle's "UEK2" kernel has also had tmem support since its release
> in early 2012.
> 
> To enable tmem support in Xen, it is necessary to specify
> a Xen boot parameter ("tmem").  Specifying "dom0_mem="

There are some extra ones too - tmem_compress tmem_dedup right?

> and disabling dom0 autoballooning in the toolstack is also
> highly recommended.  Then tmem must be explicitly enabled in
> any tmem-capable guest kernel by specifying a boot parameter
> (also "tmem") in each guest grub.conf.  Note that use of
> tmem in dom0 is not recommended, so "tmem" should not be
> provided as a dom0 boot parameter.
> 
> I'll try to write up a more complete current HOW-TO soon
> since much of the Xen tmem documentation floating around
> the web is a bit outdated.
> 
> Note that some security issues were reported in the
> Xen hypervisor tmem implementation last summer.  Please
> ensure your hypervisor is updated to patch XSA-15 before
> enabling tmem on a Xen machine exposed to the internet!
> 
> Thanks,
> Dan
> 
> P.S. If you build your own Linux guest kernels, a 3.5-or-later
> kernel is required built with the following config variables:
> 
> CONFIG_FRONTSWAP=y
> CONFIG_CLEANCACHE=y
> CONFIG_XEN_TMEM=y
> CONFIG_XEN_SELFBALLOONING=y
> 
> 
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>