Re: [PATCH 08/17] blkcg: shoot down blkio_groups on elevator switch

[Tejun Heo]

On Mon, Jan 23, 2012 at 11:28:40AM -0500, Vivek Goyal wrote:
> Can we avoid integrating everything into single blkg. What's wrong with
> separate blkg for separage policy. In this case we just don't have the
> flexbility to change throttling policy. If it is compiled in, it gets
> activated. The only configurable thing is IO scheduler and these groups
> will be cleaned up.
> 
> So keeping blkg separate for separate policy gives us this flexibility
> that we don't have to cleanup throttling data and keep the throttling
> rules persistent across elevator switch.

I think that's the wrong trade off.  We end up duplicating common
stuff all over the place and the code to deal with the mess is
naturally horrible and almost incomprehensible.  Persistency is much
more minor issue and should be handled as such.  It shouldn't contort
the whole design like it does now.  Let's talk about persistency in
the other reply.

-- 
tejun
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