Re: [PATCHv12 1/3] rdmacg: Added rdma cgroup controller

[Christoph Hellwig <hch@lst.de>]

On Thu, Sep 01, 2016 at 10:25:40AM +0300, Matan Barak wrote:
> Well, if I recall, the reason doing so last time was in order to allow 
> flexible updating of ib_core independently, which is obviously not a good 
> reason (to say the least).
>
> Since the new ABI will probably define new object types (all recent 
> proposals go this way), the current approach could lead to either trying to 
> map new objects to existing cgroup resource types, which could lead to some 
> weird non 1:1 mapping, or having a split definitions - such that each 
> driver will declare its objects both in the cgroups mechanism and in its 
> driver dispatch table.
> Even worse than that, drivers could simply ignore the cgroups support while 
> implementing their own resource types and get a very broken containers 
> support.

Sorry guys, but arbitrary extensibility for something not finished is the
worst idea ever.  We have two options here:

 a) delay cgroups support until the grand rewrite is done
 b) add it now and deal with the consequences later

That being said, adding random non-Verbs hardwasre to the RDMA core is
the second worst idea ever.  Guess I need to catch up with the
discussion and start using the flame thrower.