Re: [PATCH RFC] blkcg: prepare blkcg knobs for default hierarchy

[Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Wed, Apr 23, 2014 at 02:52:31PM -0400, Tejun Heo wrote:
> Hello,
> 
> On Wed, Apr 23, 2014 at 01:17:20PM -0400, Vivek Goyal wrote:
> > I think we should just require two. One for measuring rate in terms
> > of IOPS and other for measuring rate in terms of [kMG]B/sec.
> 
> I meant between cfq and blk-throttle.  Why do we have separate stats
> for them to present ultimately the same numbers?

Oh, sorry, I had misunderstood your question.

- Number of IOs serviced will be different at throttling layer and
  CFQ layer as throttling accounts IO in terms of bios and CFQ
  accounts in terms of number of requests.

- CFQ might not be operational on a device while throttling might be
  on and one needs bytes stats.

- In a custom kernel throttling might not be on and CFQ is on and
  one needs the stats.

So I think we do require duplication of some stats across throttling
and CFQ, isn't it?

Thanks
Vivek