linux-kernel - Re: [PATCH 6/7] psi: pressure stall information for CPU, memory, and IO

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Message-ID: <20180510142442.GG19348@cmpxchg.org>
Date:   Thu, 10 May 2018 10:24:42 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-block@...r.kernel.org, cgroups@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Mike Galbraith <efault@....de>,
        Oliver Yang <yangoliver@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        xxx xxx <x.qendo@...il.com>,
        Taras Kondratiuk <takondra@...co.com>,
        Daniel Walker <danielwa@...co.com>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Ruslan Ruslichenko <rruslich@...co.com>, kernel-team@...com
Subject: Re: [PATCH 6/7] psi: pressure stall information for CPU, memory, and
 IO

On Wed, May 09, 2018 at 12:21:00PM +0200, Peter Zijlstra wrote:
> On Mon, May 07, 2018 at 05:01:34PM -0400, Johannes Weiner wrote:
> > +	local_irq_disable();
> > +	rq = this_rq();
> > +	raw_spin_lock(&rq->lock);
> > +	rq_pin_lock(rq, &rf);
> 
> Given that churn in sched.h, you seen rq_lock() and friends.
> 
> Either write this like:
> 
> 	local_irq_disable();
> 	rq = this_rq();
> 	rq_lock(rq, &rf);
> 
> Or instroduce "rq = this_rq_lock_irq()", which we could also use in
> do_sched_yield().

Sounds good, I'll add that.

> > +	update_rq_clock(rq);
> > +
> > +	current->flags |= PF_MEMSTALL;
> > +	psi_task_change(current, rq_clock(rq), 0, TSK_MEMSTALL);
> > +
> > +	rq_unpin_lock(rq, &rf);
> > +	raw_spin_unlock(&rq->lock);
> > +	local_irq_enable();
> 
> That's called rq_unlock_irq().

I'll use that. This code was first written against a kernel that
didn't have 8a8c69c32778 ("sched/core: Add rq->lock wrappers.") yet ;)