Add the ability to define VBD QoS policy in the xend layer.
Consider the following vbd entry:
vbd = [
'phy:/dev/server/virtualmachine1-disk,xvda1,w,credit=3D5000/s@50ms',
]
This means that a VM may perform 5000 I/O operations per second, with
credit being replenished every 50 milliseconds.
The 'credit' xenstore value is by the blkback driver to ratelimit I/O
operations for the specific device.
Signed-off-by: William Pitcock <nenolod@dereferenced.org>
Keir Fraser
2ca1b6fff7