linux-kernel - Re: [RFC PATCH 07/13] sched: Add core wide task selection and scheduling.

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Message-ID: <20200522201312.GC213825@google.com>
Date:   Fri, 22 May 2020 16:13:12 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Aaron Lu <aaron.lwe@...il.com>
Cc:     vpillai <vpillai@...italocean.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, fweisbec@...il.com,
        keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>,
        Aubrey Li <aubrey.intel@...il.com>, aubrey.li@...ux.intel.com,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Aaron Lu <aaron.lu@...ux.alibaba.com>
Subject: Re: [RFC PATCH 07/13] sched: Add core wide task selection and
 scheduling.

On Fri, May 22, 2020 at 11:44:06AM +0800, Aaron Lu wrote:
[...]
> > Updated diff below:
> > 
> > ---8<-----------------------
> > 
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 005d7f7323e2d..625377f393ed3 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -182,9 +182,6 @@ static void sched_core_enqueue(struct rq *rq, struct task_struct *p)
> >  
> >  	rq->core->core_task_seq++;
> >  
> > -	if (!p->core_cookie)
> > -		return;
> > -
> >  	node = &rq->core_tree.rb_node;
> >  	parent = *node;
> >  
> > @@ -215,7 +212,7 @@ static void sched_core_dequeue(struct rq *rq, struct task_struct *p)
> >  
> >  void sched_core_add(struct rq *rq, struct task_struct *p)
> >  {
> > -	if (p->core_cookie && task_on_rq_queued(p))
> > +	if (task_on_rq_queued(p))
> >  		sched_core_enqueue(rq, p);
> >  }
> 
> It appears there are other call sites of sched_core_enqueue() where
> core_cookie is checked: cpu_cgroup_fork() and __sched_write_tag().

Thanks, but looks like pick_task()'s caller also makes various assumptions
about cookie == 0 so all that needs to be vetted again I think.

 - Joel