linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Quentin Perret <qperret@google.com>
To: Qais Yousef <qais.yousef@arm.com>
Cc: mingo@redhat.com, peterz@infradead.org,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rickyiu@google.com, wvw@google.com, patrick.bellasi@matbug.net,
	xuewen.yan94@gmail.com, linux-kernel@vger.kernel.org,
	kernel-team@android.com
Subject: Re: [PATCH v3 1/3] sched: Fix UCLAMP_FLAG_IDLE setting
Date: Thu, 1 Jul 2021 12:43:24 +0000	[thread overview]
Message-ID: <YN24bLOthLd6RIpF@google.com> (raw)
In-Reply-To: <20210701110803.2lka3eaoukbb6b4p@e107158-lin.cambridge.arm.com>

On Thursday 01 Jul 2021 at 12:08:03 (+0100), Qais Yousef wrote:
> On 07/01/21 10:07, Quentin Perret wrote:
> > On Wednesday 30 Jun 2021 at 15:45:14 (+0000), Quentin Perret wrote:
> > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > > index b094da4c5fea..c0b999a8062a 100644
> > > --- a/kernel/sched/core.c
> > > +++ b/kernel/sched/core.c
> > > @@ -980,7 +980,6 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
> > >         if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
> > >                 return;
> > > 
> > > -       rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
> > >         WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
> > >  }
> > > 
> > > @@ -1253,6 +1252,10 @@ static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
> > > 
> > >         for_each_clamp_id(clamp_id)
> > >                 uclamp_rq_inc_id(rq, p, clamp_id);
> > > +
> > > +       /* Reset clamp idle holding when there is one RUNNABLE task */
> > > +       if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
> > > +               rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
> > >  }
> > > 
> > >  static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
> > > @@ -1300,6 +1303,13 @@ uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id)
> > >         if (p->uclamp[clamp_id].active) {
> > >                 uclamp_rq_dec_id(rq, p, clamp_id);
> > >                 uclamp_rq_inc_id(rq, p, clamp_id);
> > > +
> > > +               /*
> > > +                * Make sure to clear the idle flag if we've transiently reached
> > > +                * 0 uclamp active tasks on the rq.
> > > +                */
> > > +               if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
> > > +                       rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
> > 
> > Bah, now that I had coffee I realize this has the exact same problem.
> > Let me look at this again ...
> 
> Hehe uclamp has this effect. It's all obvious, until it's not :-)

Indeed ... :)

> Yes this needs to be out of the loop.

Right or maybe we can just check that uclamp_id == UCLAMP_MAX here and
we should be good to go? That is, what about the below?


diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b094da4c5fea..8e9b8106a0df 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -980,7 +980,6 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
        if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
                return;

-       rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
        WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
 }

@@ -1253,6 +1252,10 @@ static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)

        for_each_clamp_id(clamp_id)
                uclamp_rq_inc_id(rq, p, clamp_id);
+
+       /* Reset clamp idle holding when there is one RUNNABLE task */
+       if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
+               rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
 }

 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
@@ -1300,6 +1303,13 @@ uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id)
        if (p->uclamp[clamp_id].active) {
                uclamp_rq_dec_id(rq, p, clamp_id);
                uclamp_rq_inc_id(rq, p, clamp_id);
+
+               /*
+                * Make sure to clear the idle flag if we've transiently reached
+                * 0 active tasks on rq.
+                */
+               if (clamp_id == MAX && rq->uclamp_flags & UCLAMP_FLAG_IDLE)
+                       rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
        }

        task_rq_unlock(rq, p, &rf);

  reply	other threads:[~2021-07-01 12:43 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 12:34 [PATCH v3 0/3] sched: A few uclamp fixes and tweaks Quentin Perret
2021-06-23 12:34 ` [PATCH v3 1/3] sched: Fix UCLAMP_FLAG_IDLE setting Quentin Perret
2021-06-30 14:58   ` Qais Yousef
2021-06-30 15:45     ` Quentin Perret
2021-07-01 10:07       ` Quentin Perret
2021-07-01 11:08         ` Qais Yousef
2021-07-01 12:43           ` Quentin Perret [this message]
2021-07-01 14:57             ` Qais Yousef
2021-07-01 15:20               ` Quentin Perret
2021-07-01 17:59                 ` Qais Yousef
2021-07-02 11:54                   ` Quentin Perret
2021-07-01 11:06       ` Qais Yousef
2021-06-23 12:34 ` [PATCH v3 2/3] sched: Skip priority checks with SCHED_FLAG_KEEP_PARAMS Quentin Perret
2021-06-30 16:01   ` Qais Yousef
2021-06-23 12:34 ` [PATCH v3 3/3] sched: Introduce RLIMIT_UCLAMP Quentin Perret
2021-07-01 10:50   ` Qais Yousef
2021-07-01 12:05     ` Quentin Perret
2021-07-01 17:52       ` Qais Yousef
2021-07-02 12:28         ` Quentin Perret
2021-07-08 11:36           ` Qais Yousef
2021-07-19 11:44             ` Quentin Perret
2021-07-26 16:22               ` Qais Yousef

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YN24bLOthLd6RIpF@google.com \
    --to=qperret@google.com \
    --cc=dietmar.eggemann@arm.com \
    --cc=kernel-team@android.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=patrick.bellasi@matbug.net \
    --cc=peterz@infradead.org \
    --cc=qais.yousef@arm.com \
    --cc=rickyiu@google.com \
    --cc=vincent.guittot@linaro.org \
    --cc=wvw@google.com \
    --cc=xuewen.yan94@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).