Re: [Libguestfs] [PATCH supermin] Add support for a DAX root filesystem.
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.
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Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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