linux-kernel - Re: [RFD/RFC PATCH 4/8] sched: Split scheduler execution context

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Message-ID: <20190506110628.GA5016@erbrow>
Date:   Mon, 6 May 2019 13:06:29 +0200
From:   Claudio Scordino <claudio@...dence.eu.com>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     peterz@...radead.org, mingo@...hat.com, rostedt@...dmis.org,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        luca.abeni@...tannapisa.it, tommaso.cucinotta@...tannapisa.it,
        alessio.balsini@...il.com, bristot@...hat.com, will.deacon@....com,
        andrea.parri@...rulasolutions.com, dietmar.eggemann@....com,
        patrick.bellasi@....com, henrik@...tad.us,
        linux-rt-users@...r.kernel.org
Subject: Re: [RFD/RFC PATCH 4/8] sched: Split scheduler execution context

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@...radead.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@...radead.org>
> [added lot of comments/questions - identifiable by XXX]
> Signed-off-by: Juri Lelli <juri.lelli@...hat.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