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Re: [Xen-users] I/O and Network control on VM

  • To: Xen User-List <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: Thomas Goirand <thomas@xxxxxxxxxx>
  • Date: Sun, 14 Jun 2009 00:09:36 +0800
  • Delivery-date: Sat, 13 Jun 2009 09:10:27 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Openpgp: id=98EF9A49

Fajar A. Nugraha wrote:
> Thomas, I assume you're referring to using cbq to do rate limit
> (providing similar functionality as Xen's rate limit)?


> Or are you saying that cbq can limit daily transfer as per the
> original requirement?

No, such limits can be done only by tight accounting of bandwidth.

>>>> 2. How about I/O limit? Seem xen currently has no way to limit user I/O 
>>>> usage?
>>> Your best bet (for now) is probably something like
>>> http://people.valinux.co.jp/~ryov/dm-ioband/
>> There's no need to apply any patch to acheive I/O scheduling, it has
>> been in the kernel for YEARS.
> Care to provide some reference/example on how this can be used on dom0
> to limit domU's I/O usage?

Let's say you have a domU with ID 39, it will use blkback.39.sda1 and
blkback.39.sda2 let's say. Use ionice to give priorities to the process
ID of blkback.39.sda1. It's not limits per say, but it's priorities,
which is quite cool already. If someone is using too much I/O, just give
the process the lowest priority possible, and it wont bother others too

By the way, is it that the above mentioned patch is adding
max_hw_sectors_kb and max_sectors_kb in /sys/block/dm-XX/queue, like it
is available for other block devices? If yes, that's pretty cool, and I
wonder why it hasn't been merged with mainline kernel...


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