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[35.195.168.105]) by smtp.gmail.com with ESMTPSA id v1sm1995241wre.20.2021.07.01.05.43.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Jul 2021 05:43:27 -0700 (PDT) Date: Thu, 1 Jul 2021 12:43:24 +0000 From: Quentin Perret To: Qais Yousef 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 Message-ID: References: <20210623123441.592348-1-qperret@google.com> <20210623123441.592348-2-qperret@google.com> <20210630145848.htb7pnwsl2gao77x@e107158-lin.cambridge.arm.com> <20210701110803.2lka3eaoukbb6b4p@e107158-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210701110803.2lka3eaoukbb6b4p@e107158-lin.cambridge.arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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);