Re[2]: [Xen-users] Re: [Xen-devel] VM disk I/O limit patch

[Andrew Xu <xu.an@xxxxxxxxxx>]

On Wed, 22 Jun 2011 09:11:21 -0400
Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:

> On Wed, Jun 22, 2011 at 08:06:23PM +0800, Andrew Xu wrote:
> > 
> > On Tue, 21 Jun 2011 09:33:37 -0400
> > Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
> > 
> > > On Tue, Jun 21, 2011 at 04:29:35PM +0800, Andrew Xu wrote:
> > > > Hi all,
> > > > 
> > > > I add a blkback QoS patch.
> > > 
> > > What tree is this against? 
> > This patch is based on suse11.sp1(2.6.32) xen-blkback source. 
> > (2.6.18 "Xenlinux" based source trees?)
> > 
> > > There is a xen-blkback in 3.0-rc4, can you rebase
> > > it against that please.
> > > 
> > Ok, I will rebase it.
> 
> Hold on, lets talk about the problem you are trying to solve first.
> > 
> > > What is the patch solving? 
> > > 
> > With this path, you can set different speed I/O for different VM disk.
> > For example, I set vm17-disk1 4MKB/s 
> >                    vm17-disk2 1MKB/s 
> >                    vm18-disk3 3MKB/s 
> > I/O speed, by writing follow xenstore key-values.
> >     /local/domain/17/device/vbd/768/tokens-rate = "4096"
> >     /local/domain/17/device/vbd/2048/tokens-rate = "1024"
> >     /local/domain/18/device/vbd/768/tokens-rate = "3096"
> > 
> > > Why can't it be done with dm-ioband?
> > Of cause, I/O speed limit also can be done with dm-ioband.
> > But with my patch, there is no need to load dm-ioband any more.
> > This patch do speed-limit more close disk, more lightweight.
> 
> 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?



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