linux-kernel - Re: [RFC 5/8] Track the "total rq utilisation" too

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Message-ID: <20160115101511.726cfe29@luca-1225C>
Date:	Fri, 15 Jan 2016 10:15:11 +0100
From:	Luca Abeni <luca.abeni@...tn.it>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@....com>
Subject: Re: [RFC 5/8] Track the "total rq utilisation" too

On Fri, 15 Jan 2016 09:34:00 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On Fri, Jan 15, 2016 at 07:50:49AM +0100, Luca Abeni wrote:
> > On Thu, 14 Jan 2016 20:48:37 +0100
> > Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > On Thu, Jan 14, 2016 at 04:24:50PM +0100, Luca Abeni wrote:
> > > > This is the sum of the utilisations of tasks that are assigned
> > > > to a runqueue, independently from their state (TASK_RUNNING or
> > > > blocked)
> > > 
> > > Is it actually used?
> > Not in this patchset...
> > It is a possible "cheap" (but less accurate) alternative to the
> > tracking introduced in patch 4. Or can be used in more advanced
> > implementations of multi-processor GRUB, but not in this patchset.
> > 
> > So, it can be removed from the patchset; I added it so that people
> > can see all the possible alternative utilization tracking
> > strategies.
> 
> OK, so that might've been useful text for the changelog. But given
> that, maybe leave it out for now.
> 
> BTW, have you got a paper on smp grub?
The one mentioned in the cover letter describes the implementation I
posted:
http://disi.unitn.it/~abeni/reclaiming/rtlws14-grub.pdf

There is also a newer paper, that will be published at ACM SAC 2016
(so, it is not available yet), but is based on this technical report:
http://arxiv.org/abs/1512.01984
This second paper describes some more complex algorithms (easily
implementable over this patchset) that are able to guarantee hard
schedulability for SCHED_DEADLINE tasks with reclaiming on SMP.



				Luca