Re: [PATCH 2/3] i/o bandwidth controller infrastructure

[Andrew Morton]

On Fri, 27 Jun 2008 00:36:46 +0200
Andrea Righi <righi.andrea@xxxxxxxxx> wrote:

> > Does all this code treat /dev/sda1 as a separate device from /dev/sda2?
> >  If so, that would be broken.
> 
> Yes, all the partitions are treated as separate devices with
> (potentially) different limiting rules, but I don't understand why it
> would be broken... dev_t has both minor and major numbers, so it would
> be possible to select single partitions as well.

Well it's functionally broken, isn't it?  A physical disk has a fixed
IO bandwidth and when the administrator wants to partition that
bandwidth amongst control groups he will need to consider the entire
device when doing so?

I mean, the whole point of this feature and of control groups as a
whole is isolation.  But /dev/sda1 and /dev/sda2 are very much _not_
isolated.  Whereas /dev/sda and /dev/sdb are (to a large degree)
isolated.

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