Re: [Xen-users] Re: VM disk I/O limit patch

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> > I am not convienced this will be easier to maintain than
> > using existing code (dm-ioband) that Linux kernel provides already.
> > 
> > Are there other technical reasons 'dm-ioband' is not sufficient
> > enough? Could it be possible to fix 'dm-ioband' to not have those
> > bugs? Florian mentioned flush requests not passing through
> > the DM layers but I am pretty sure those have been fixed.
> > 
> I don't find dm-ioband's bug, so I can't answer your question.
> 
> But, xen-vm-disk I/O limitation shoud done by xen module, is not it?

Not all I/O's for a guest go through the xen-blkback. For example
the tap, qcow, are all inside of QEMU which has no notion of xen-blkback
(this is upstream QEMU BTW) - so they would not benefit from this
at all.

While if all of the "disks" that are assigned to a guest go
through dm-ioband the system admin has only one interface that can cover
_all_ of the I/O sinks. And it is standard enough so that if that
system admin is switching over from KVM to Xen they don't have to
alter a lot of their infrastructure.