From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0EFA6C433EF for ; Thu, 21 Jul 2022 14:19:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229506AbiGUOT0 (ORCPT ); Thu, 21 Jul 2022 10:19:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229462AbiGUOTY (ORCPT ); Thu, 21 Jul 2022 10:19:24 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7718D8048A for ; Thu, 21 Jul 2022 07:19:23 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BF2A71042; Thu, 21 Jul 2022 07:19:23 -0700 (PDT) Received: from wubuntu (unknown [10.57.86.173]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9AEA73F73D; Thu, 21 Jul 2022 07:19:20 -0700 (PDT) Date: Thu, 21 Jul 2022 15:19:18 +0100 From: Qais Yousef To: Xuewen Yan Cc: Ingo Molnar , "Peter Zijlstra (Intel)" , Vincent Guittot , Dietmar Eggemann , linux-kernel@vger.kernel.org, Wei Wang , Jonathan JMChen , Hank , Yun Hsiang Subject: Re: [PATCH 3/7] sched/uclamp: Fix fits_capacity() check in feec() Message-ID: <20220721141918.s2xlvrwqvulp6lyb@wubuntu> References: <20220629194632.1117723-1-qais.yousef@arm.com> <20220629194632.1117723-4-qais.yousef@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/20/22 15:30, Xuewen Yan wrote: > Hi Qais > > On Thu, Jun 30, 2022 at 3:48 AM Qais Yousef wrote: > > > > As reported by Yun Hsiang [1], if a task has its uclamp_min >= 0.8 * 1024, > > it'll always pick the previous CPU because fits_capacity() will always > > return false in this case. > > > > The new util_fits_cpu() logic should handle this correctly for us beside > > more corner cases where similar failures could occur, like when using > > UCLAMP_MAX. > > > > We open code uclamp_rq_util_with() except for the clamp() part, > > util_fits_cpu() needs the 'raw' values to be passed to it. > > > > Also introduce uclamp_rq_{set, get}() shorthand accessors to get uclamp > > value for the rq. Makes the code more readable and ensures the right > > rules (use READ_ONCE/WRITE_ONCE) are respected transparently. > > > > [1] https://lists.linaro.org/pipermail/eas-dev/2020-July/001488.html > > > > Fixes: 1d42509e475c ("sched/fair: Make EAS wakeup placement consider uclamp restrictions") > > Reported-by: Yun Hsiang > > Signed-off-by: Qais Yousef > > --- > > kernel/sched/core.c | 10 +++++----- > > kernel/sched/fair.c | 26 ++++++++++++++++++++++++-- > > kernel/sched/sched.h | 40 ++++++++++++++++++++++++++++++++++++++-- > > 3 files changed, 67 insertions(+), 9 deletions(-) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index d3e2c5a7c1b7..f5dac570d6c5 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -1404,7 +1404,7 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id, > > if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE)) > > return; > > > > - WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value); > > + uclamp_rq_set(rq, clamp_id, clamp_value); > > } > > > > static inline > > @@ -1555,8 +1555,8 @@ static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p, > > if (bucket->tasks == 1 || uc_se->value > bucket->value) > > bucket->value = uc_se->value; > > > > - if (uc_se->value > READ_ONCE(uc_rq->value)) > > - WRITE_ONCE(uc_rq->value, uc_se->value); > > + if (uc_se->value > uclamp_rq_get(rq, clamp_id)) > > + uclamp_rq_set(rq, clamp_id, uc_se->value); > > } > > > > /* > > @@ -1622,7 +1622,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p, > > if (likely(bucket->tasks)) > > return; > > > > - rq_clamp = READ_ONCE(uc_rq->value); > > + rq_clamp = uclamp_rq_get(rq, clamp_id); > > /* > > * Defensive programming: this should never happen. If it happens, > > * e.g. due to future modification, warn and fixup the expected value. > > @@ -1630,7 +1630,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p, > > SCHED_WARN_ON(bucket->value > rq_clamp); > > if (bucket->value >= rq_clamp) { > > bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value); > > - WRITE_ONCE(uc_rq->value, bkt_clamp); > > + uclamp_rq_set(rq, clamp_id, bkt_clamp); > > } > > } > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 313437bea5a2..c80c676ab1bc 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -6878,6 +6878,8 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd) > > static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) > > { > > unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX; > > + unsigned long p_util_min = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MIN) : 0; > > + unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024; > > struct root_domain *rd = cpu_rq(smp_processor_id())->rd; > > int cpu, best_energy_cpu = prev_cpu, target = -1; > > unsigned long cpu_cap, util, base_energy = 0; > > @@ -6907,6 +6909,8 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) > > > > for (; pd; pd = pd->next) { > > unsigned long cur_delta, spare_cap, max_spare_cap = 0; > > + unsigned long rq_util_min, rq_util_max; > > + unsigned long util_min, util_max; > > bool compute_prev_delta = false; > > unsigned long base_energy_pd; > > int max_spare_cap_cpu = -1; > > @@ -6927,8 +6931,26 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) > > * much capacity we can get out of the CPU; this is > > * aligned with sched_cpu_util(). > > */ > > - util = uclamp_rq_util_with(cpu_rq(cpu), util, p); > > - if (!fits_capacity(util, cpu_cap)) > > + if (uclamp_is_used()) { > > + if (uclamp_rq_is_idle(cpu_rq(cpu))) { > > + util_min = p_util_min; > > + util_max = p_util_max; > > + } else { > > + /* > > + * Open code uclamp_rq_util_with() except for > > + * the clamp() part. Ie: apply max aggregation > > + * only. util_fits_cpu() logic requires to > > + * operate on non clamped util but must use the > > + * max-aggregated uclamp_{min, max}. > > + */ > > + rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN); > > + rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX); > > + > > + util_min = max(rq_util_min, p_util_min); > > + util_max = max(rq_util_max, p_util_max); > > + } > > + } > > + if (!util_fits_cpu(util, util_min, util_max, cpu)) > > continue; > > > > if (cpu == prev_cpu) { > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > > index 9599d2eea3e7..69c4d35988b9 100644 > > --- a/kernel/sched/sched.h > > +++ b/kernel/sched/sched.h > > @@ -2907,6 +2907,23 @@ static inline unsigned long cpu_util_rt(struct rq *rq) > > #ifdef CONFIG_UCLAMP_TASK > > unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id); > > > > +static inline unsigned long uclamp_rq_get(struct rq *rq, > > + enum uclamp_id clamp_id) > > +{ > > + return READ_ONCE(rq->uclamp[clamp_id].value); > > +} > > + > > +static inline void uclamp_rq_set(struct rq *rq, enum uclamp_id clamp_id, > > + unsigned int value) > > +{ > > + WRITE_ONCE(rq->uclamp[clamp_id].value, value); > > +} > > + > > +static inline bool uclamp_rq_is_idle(struct rq *rq) > > +{ > > + return rq->uclamp_flags & UCLAMP_FLAG_IDLE; > > +} > > Can you replace the idle judgment in the uclamp_rq_util_with() > function by the way? Yep I missed it. Fixed. Thanks! -- Qais Yousef