[PATCH 0/2] RFC: Implement I/O QoS in dom0

[William Pitcock <nenolod@dereferenced.org>]

Greetings,

This patch series against xen.git implements a nieve token-based QoS
limiter for I/O accesses using blkback. The idea is to ensure a fair
share of disk I/O resources to all guests on the machine. Right now
if you have a setup involving AoE, ensuring guest reliability is much
more complex because the AoE layer bypasses the system scheduler.

This patchset intends to add simple QoS limits. It was inspired by the
'token-limiter' patch for UML, which is quite effective for limiting
I/O usage. However, since the limits are enforced by the host, this means
that users cannot get around the QoS limits by using a different kernel.

This work is not yet complete, see my commit commentary for things that
need to be done.

Mostly right now we need to consider whether a sysctl interface or a
sysfs interface would be best to implement for tweaking the blkback
limits.

Also please note that all of this applies to paravirtualized guests only,
HVM guests go through qemu-dm, which can be effectively limited using
ionice.

Please also note that this is a test patch only, and is not the final
version. Commentary and discussion of this patch and ways that it could be
changed/improved would be desirable.

William Pitcock (2):
  blkback: Implement VBD QoS mechanics.
  blkback: Add default policy values for I/O QoS code

 drivers/xen/blkback/blkback.c   |   22 ++++++++++++++++++++++
 drivers/xen/blkback/common.h    |    6 ++++++
 drivers/xen/blkback/interface.c |    9 +++++++++
 3 files changed, 37 insertions(+), 0 deletions(-)