linux-kernel - Re: [PATCH 1/2] sched/deadline: add per rq tracking of admitted bandwidth

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Message-ID: <20160225102034.GE6357@twins.programming.kicks-ass.net>
Date:	Thu, 25 Feb 2016 11:20:34 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	luca abeni <luca.abeni@...tn.it>, linux-kernel@...r.kernel.org,
	mingo@...hat.com, vincent.guittot@...aro.org,
	wanpeng.li@...mail.com
Subject: Re: [PATCH 1/2] sched/deadline: add per rq tracking of admitted
 bandwidth

On Thu, Feb 25, 2016 at 10:07:06AM +0000, Juri Lelli wrote:
> Argh, this makes lot of sense to me. I've actually pondered a tree/list
> solution, but then decided to try the cumulative approach because it
> looked nicer. But it contains holes, I'm afraid. As Luca already said,
> GRUB shouldn't have these problems though.
> 
> I'll try and see what introducting a list of blocked/throttled deadline
> tasks means, considering also the interaction with cpusets and such.
> Maybe it's simpler than it seems.
> 
> I'm not sure this will come anytime soon, unfortunately. I'm almost 100%
> on the sched-freq/schedutil discussion these days.

Just skip sleep and write them when its dark outside :-)

> Anyway, do you also think that what we want to solve the root domain
> issue is something based on rq_online/offline and per-rq information?
> Everything else that I tried or thought of was broken/more horrible. :-/

I was still trying to get my head around this, the above was my
suggestion to the per-rq state, but I've not thought hard on alternative
approaches to the root_domain issue.