Messages in this thread | | | From | Xuewen Yan <> | Date | Wed, 20 Jul 2022 15:30:58 +0800 | Subject | Re: [PATCH 3/7] sched/uclamp: Fix fits_capacity() check in feec() |
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Hi Qais
On Thu, Jun 30, 2022 at 3:48 AM Qais Yousef <qais.yousef@arm.com> 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 <hsiang023167@gmail.com> > Signed-off-by: Qais Yousef <qais.yousef@arm.com> > --- > 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?
> + > /** > * uclamp_rq_util_with - clamp @util with @rq and @p effective uclamp values. > * @rq: The rq to clamp against. Must not be NULL. > @@ -2946,8 +2963,8 @@ unsigned long uclamp_rq_util_with(struct rq *rq, unsigned long util, > goto out; > } > > - min_util = max_t(unsigned long, min_util, READ_ONCE(rq->uclamp[UCLAMP_MIN].value)); > - max_util = max_t(unsigned long, max_util, READ_ONCE(rq->uclamp[UCLAMP_MAX].value)); > + min_util = max_t(unsigned long, min_util, uclamp_rq_get(rq, UCLAMP_MIN)); > + max_util = max_t(unsigned long, max_util, uclamp_rq_get(rq, UCLAMP_MAX)); > out: > /* > * Since CPU's {min,max}_util clamps are MAX aggregated considering > @@ -3010,6 +3027,25 @@ static inline bool uclamp_is_used(void) > { > return false; > } > + > +static inline unsigned long uclamp_rq_get(struct rq *rq, > + enum uclamp_id clamp_id) > +{ > + if (clamp_id == UCLAMP_MIN) > + return 0; > + > + return SCHED_CAPACITY_SCALE; > +} > + > +static inline void uclamp_rq_set(struct rq *rq, enum uclamp_id clamp_id, > + unsigned int value) > +{ > +} > + > +static inline bool uclamp_rq_is_idle(struct rq *rq) > +{ > + return false; > +} > #endif /* CONFIG_UCLAMP_TASK */ > > #ifdef CONFIG_HAVE_SCHED_AVG_IRQ > -- > 2.25.1 >
Thanks! BR ---- xuewen.yan
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