[PATCH 0 of 9] Xen support for Remus

[Brendan Cully <brendan@cs.ubc.ca>]

Hi all,

This set of patches adds Remus support to Xen.

Remus extends the Xen live migration machinery in order to provide
transparent, comprehensive high availability for ordinary virtual
machines. More information can be found at
<http://dsg.cs.ubc.ca/remus/>.

This patch set is against the current tip of xen-unstable (changeset
2522cc95efd2). It provides support for PV guests in 32-on-32 and
64-on-64 configurations -- 32-on-64 and HVM are still in progress.

These patches modify Xen to support Remus -- to actually use it,
you'll also need the control tools and instructions available here:
http://dsg.cs.ubc.ca/remus/hg/tools/
I'll investigate integrating the tool stack into the Xen repository's
'tools' directory soon.

I've tested these changes for backward compatibility with unpatched
Xen. Specifically, I've tested live migration in both directions (from
plain Xen to Remusified Xen and vice versa) for PV and HVM guests,
each in 32-on-32, 32-on-64, and 64-on-64 configurations.

I'm maintaining these patches in an hg queue repository here:
http://dsg.cs.ubc.ca/remus/hg/xen-3.4-testing.hg/patches/

Details of the patch series:

The first two patches provide core support for incremental
checkpointing:

continuous-checkpoint
continuous-restore

The next 3 provide a new tapdisk module ('remus') which acts as a
proxy for any other tapdisk module, replicating writes to the backup
node:

tapdisk-more-fds
tapdisk-image-check
tapdisk-remus

All following patches are performance related.

These patches are a request for comment, and as such are optimized to
be easy to rebase rather than beautiful, but I'm happy to discuss how
they could be polished. With that in mind, I hope that you'll try them
out if you're interested in high availability or fast, incremental
checkpointing in general. I look forward to your feedback!

Brendan