Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 6 May 2019 13:06:29 +0200
From:   Claudio Scordino <claudio@evidence.eu.com>
To:     Juri Lelli <juri.lelli@redhat.com>
Cc:     peterz@infradead.org, mingo@redhat.com, rostedt@goodmis.org,
        tglx@linutronix.de, linux-kernel@vger.kernel.org,
        luca.abeni@santannapisa.it, tommaso.cucinotta@santannapisa.it,
        alessio.balsini@gmail.com, bristot@redhat.com, will.deacon@arm.com,
        andrea.parri@amarulasolutions.com, dietmar.eggemann@arm.com,
        patrick.bellasi@arm.com, henrik@austad.us,
        linux-rt-users@vger.kernel.org
Subject: Re: [RFD/RFC PATCH 4/8] sched: Split scheduler execution context
Message-ID: <20190506110628.GA5016@erbrow>
References: <20181009092434.26221-1-juri.lelli@redhat.com>
 <20181009092434.26221-5-juri.lelli@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20181009092434.26221-5-juri.lelli@redhat.com>
User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Dear Juri,

just a small comment for the next round of patches (I guess after
OSPM)...


On 091018, 11:24, Juri Lelli wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> 
> Lets define the scheduling context as all the scheduler state in
> task_struct and the execution context as all state required to run the
> task.
> 
> Currently both are intertwined in task_struct. We want to logically
> split these such that we can run the execution context of one task
> with the scheduling context of another.
> 
> To this purpose introduce rq::proxy to point to the task_struct used
> for scheduler state and preserve rq::curr to denote the execution
> context.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> [added lot of comments/questions - identifiable by XXX]
> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
> ---
>  kernel/sched/core.c  | 62 ++++++++++++++++++++++++++++++++++----------
>  kernel/sched/fair.c  |  4 +++
>  kernel/sched/sched.h | 30 ++++++++++++++++++++-
>  3 files changed, 82 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index fe0223121883..d3c481b734dd 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -224,12 +224,13 @@ static enum hrtimer_restart hrtick(struct hrtimer *timer)
>  {
>  	struct rq *rq = container_of(timer, struct rq, hrtick_timer);
>  	struct rq_flags rf;
> +	struct task_struct *curr = rq->proxy;

You may want to use a different naming for these local variables (e.g.
"proxy") to help the reader in not confusing curr (i.e. scheduling ctx)
with rq::curr (i.e. execution ctx).

Best regards,

               Claudio