Re: [PATCH RFC 10/22] block, bfq: add full hierarchical scheduling and cgroups support

[Tejun Heo]

Hello, Paolo.

On Fri, Apr 22, 2016 at 08:19:47PM +0200, Paolo Valente wrote:
> > So, a kworker would jump through different workqueues and issue IOs
> > for different writeback domains and the context can't be tied to the
> > issuing task.  The cgroup membership should be determined directly
> > from the bio.
> 
> Yes. My doubt arises from the fact that the only source of intense I/O
> is the dd (I have executed it alone). In contrast, group changes occur
> at a high frequency during all the execution of the dd. Apparently I
> cannot see any other I/O induced by the dd. Journaling issues sync
> requests.
> 
> >  cfq uses per-cgroup async queue.  I'm not sure how this
> > would map to bfq tho.
> 
> Itâs the same. But this is the part Iâm checking.

Ah, right, I was confused.  cic is always associated with the task and
yes a writeback worker can trigger blkcg changed events frequently as
it walks through different cgroups.  Is this an issue?

Thanks.

-- 
tejun