[Libguestfs] [PATCH supermin] Add support for a DAX root filesystem.

Richard W.M. Jones rjones at redhat.com
Tue May 17 08:01:38 UTC 2016


On Mon, May 16, 2016 at 07:09:44PM +0100, Richard W.M. Jones wrote:
> DAX is explained in detail here:
> https://lwn.net/Articles/610174/
> 
> This patch adds support to supermin for using a DAX root filesystem.
> The corresponding libguestfs patches will be posted shortly once I've
> tested them a bit more.
> 
> This requires qemu >= 2.6.
> 
> Unfortunately it's not really a win for a few reasons:
> 
>  - Requires enabling ACPI, which slows everything down by hundreds of
>    milliseconds.  I need to work out exactly what's going on here.
>    Since we never required ACPI before now, I never had the impetus to
>    find out if this is easy to fix.

Good news is I have fixed the ACPI issue.  The slowdown is now
very minor (< 20ms).

Rich.

>  - The extra modules in the supermin mini-initrd greatly increase its
>    size, which also slows things down.  qemu fw_cfg DMA should help
>    here, if we ever manage to get it upstream.
> 
>  - vNVDIMM and DAX are not very widely tested or used yet.
> 
>  - Not supported at all by libvirt.
> 
> Rich.
> 
> _______________________________________________
> Libguestfs mailing list
> Libguestfs at redhat.com
> https://www.redhat.com/mailman/listinfo/libguestfs

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v




More information about the Libguestfs mailing list