linux-kernel - Re: [PATCH 01/10] sched/deadline: track the active utilization

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Message-ID: <20170608093634.530fcfa7@gandalf.local.home>
Date:   Thu, 8 Jun 2017 09:36:34 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Juri Lelli <juri.lelli@....com>
Cc:     Luca Abeni <luca.abeni@...tannapisa.it>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Luca Abeni <luca.abeni@...tn.it>
Subject: Re: [PATCH 01/10] sched/deadline: track the active utilization

On Thu, 8 Jun 2017 10:05:55 +0100
Juri Lelli <juri.lelli@....com> wrote:

> On 08/06/17 10:43, Luca Abeni wrote:
> > On Thu, 8 Jun 2017 10:31:25 +0200
> > Ingo Molnar <mingo@...nel.org> wrote:
> >   
> > > * luca abeni <luca.abeni@...tannapisa.it> wrote:
> > >   
> > > > From: Luca Abeni <luca.abeni@...tn.it>
> > > > 
> > > > Active utilization is defined as the total utilization of active
> > > > (TASK_RUNNING) tasks queued on a runqueue. Hence, it is increased
> > > > when a task wakes up and is decreased when a task blocks.
> > > > 
> > > > When a task is migrated from CPUi to CPUj, immediately subtract the
> > > > task's utilization from CPUi and add it to CPUj. This mechanism is
> > > > implemented by modifying the pull and push functions.
> > > > Note: this is not fully correct from the theoretical point of view
> > > > (the utilization should be removed from CPUi only at the 0 lag
> > > > time), a more theoretically sound solution is presented in the
> > > > next patches.
> > > > 
> > > > Signed-off-by: Juri Lelli <juri.lelli@....com>
> > > > Signed-off-by: Luca Abeni <luca.abeni@...tn.it>
> > > > Tested-by: Daniel Bristot de Oliveira <bristot@...hat.com>    
> > > 
> > > So that SOB chain is not valid - either Juri needs to be the From:
> > > author, or it should be an Acked-by (or Reviewed-by).
> > > 
> > > For now I've converted this to:
> > >   
> > > > Signed-off-by: Luca Abeni <luca.abeni@...tn.it>
> > > > Acked-by: Juri Lelli <juri.lelli@....com>    
> > 
> > Sorry, my fault: I must have misunderstood how to use the Signed-off-by
> > stuff.
> > 
> > The story here is that I took a patch originally developed by Juri and
> > fixed and I heavily modified it. Since the current patch is very
> > different from the original one, Juri suggested I should by the "From:"
> > author, and I simply added his Signed-off-by to acknowledge that he was
> > the author of the original patch.
> > 
> > If Juri is ok with your change, I agree with it.
> >   
> 
> Yep, I'm OK with Ingo's solution.
> 

Although, since the code originally came from you a Signed-off-by is
appropriate. The SOB is a chain of where the patch came from. As Juri
actually has part ownership, Juri should have a signed-off-by on the
patch. The problem with git is that it allows for multiple signed off
bys but only one owner.

-- Steve