sched/fair: Refactor CPU utilization functions
There is a lot of code duplication in cpu_util_next() & cpu_util_cfs(). Remove this by allowing cpu_util_next() to be called with p = NULL. Rename cpu_util_next() to cpu_util() since the '_next' suffix is no longer necessary to distinct cpu utilization related functions. Implement cpu_util_cfs(cpu) as cpu_util(cpu, p = NULL, -1). This will allow to code future related cpu util changes only in one place, namely in cpu_util(). Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20230515115735.296329-2-dietmar.eggemann@arm.com
This commit is contained in:
Dietmar Eggemann
Peter Zijlstra
Родитель
e6a15fa9ea
Коммит
3eb6d6ecec
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@ -7202,11 +7202,41 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
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return target;
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}
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/*
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* Predicts what cpu_util(@cpu) would return if @p was removed from @cpu
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* (@dst_cpu = -1) or migrated to @dst_cpu.
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/**
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* cpu_util() - Estimates the amount of CPU capacity used by CFS tasks.
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* @cpu: the CPU to get the utilization for
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* @p: task for which the CPU utilization should be predicted or NULL
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* @dst_cpu: CPU @p migrates to, -1 if @p moves from @cpu or @p == NULL
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*
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* The unit of the return value must be the same as the one of CPU capacity
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* so that CPU utilization can be compared with CPU capacity.
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*
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* CPU utilization is the sum of running time of runnable tasks plus the
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* recent utilization of currently non-runnable tasks on that CPU.
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* It represents the amount of CPU capacity currently used by CFS tasks in
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* the range [0..max CPU capacity] with max CPU capacity being the CPU
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* capacity at f_max.
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*
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* The estimated CPU utilization is defined as the maximum between CPU
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* utilization and sum of the estimated utilization of the currently
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* runnable tasks on that CPU. It preserves a utilization "snapshot" of
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* previously-executed tasks, which helps better deduce how busy a CPU will
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* be when a long-sleeping task wakes up. The contribution to CPU utilization
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* of such a task would be significantly decayed at this point of time.
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*
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* CPU utilization can be higher than the current CPU capacity
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* (f_curr/f_max * max CPU capacity) or even the max CPU capacity because
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* of rounding errors as well as task migrations or wakeups of new tasks.
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* CPU utilization has to be capped to fit into the [0..max CPU capacity]
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* range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%)
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* could be seen as over-utilized even though CPU1 has 20% of spare CPU
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* capacity. CPU utilization is allowed to overshoot current CPU capacity
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* though since this is useful for predicting the CPU capacity required
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* after task migrations (scheduler-driven DVFS).
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*
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* Return: (Estimated) utilization for the specified CPU.
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*/
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static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
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static unsigned long cpu_util(int cpu, struct task_struct *p, int dst_cpu)
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{
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struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
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unsigned long util = READ_ONCE(cfs_rq->avg.util_avg);
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@ -7217,9 +7247,9 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
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* contribution. In all the other cases @cpu is not impacted by the
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* migration so its util_avg is already correct.
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*/
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if (task_cpu(p) == cpu && dst_cpu != cpu)
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if (p && task_cpu(p) == cpu && dst_cpu != cpu)
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lsub_positive(&util, task_util(p));
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else if (task_cpu(p) != cpu && dst_cpu == cpu)
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else if (p && task_cpu(p) != cpu && dst_cpu == cpu)
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util += task_util(p);
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if (sched_feat(UTIL_EST)) {
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@ -7255,7 +7285,7 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
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*/
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if (dst_cpu == cpu)
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util_est += _task_util_est(p);
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else if (unlikely(task_on_rq_queued(p) || current == p))
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else if (p && unlikely(task_on_rq_queued(p) || current == p))
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lsub_positive(&util_est, _task_util_est(p));
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util = max(util, util_est);
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@ -7264,6 +7294,11 @@ static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
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return min(util, capacity_orig_of(cpu));
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}
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unsigned long cpu_util_cfs(int cpu)
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{
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return cpu_util(cpu, NULL, -1);
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}
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/*
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* cpu_util_without: compute cpu utilization without any contributions from *p
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* @cpu: the CPU which utilization is requested
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@ -7281,9 +7316,9 @@ static unsigned long cpu_util_without(int cpu, struct task_struct *p)
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{
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/* Task has no contribution or is new */
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if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
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return cpu_util_cfs(cpu);
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p = NULL;
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return cpu_util_next(cpu, p, -1);
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return cpu_util(cpu, p, -1);
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}
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/*
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@ -7330,7 +7365,7 @@ static inline void eenv_task_busy_time(struct energy_env *eenv,
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* cpu_capacity.
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*
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* The contribution of the task @p for which we want to estimate the
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* energy cost is removed (by cpu_util_next()) and must be calculated
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* energy cost is removed (by cpu_util()) and must be calculated
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* separately (see eenv_task_busy_time). This ensures:
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*
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* - A stable PD utilization, no matter which CPU of that PD we want to place
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@ -7351,7 +7386,7 @@ static inline void eenv_pd_busy_time(struct energy_env *eenv,
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int cpu;
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for_each_cpu(cpu, pd_cpus) {
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unsigned long util = cpu_util_next(cpu, p, -1);
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unsigned long util = cpu_util(cpu, p, -1);
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busy_time += effective_cpu_util(cpu, util, ENERGY_UTIL, NULL);
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}
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@ -7375,7 +7410,7 @@ eenv_pd_max_util(struct energy_env *eenv, struct cpumask *pd_cpus,
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for_each_cpu(cpu, pd_cpus) {
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struct task_struct *tsk = (cpu == dst_cpu) ? p : NULL;
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unsigned long util = cpu_util_next(cpu, p, dst_cpu);
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unsigned long util = cpu_util(cpu, p, dst_cpu);
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unsigned long cpu_util;
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/*
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@ -7521,7 +7556,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
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if (!cpumask_test_cpu(cpu, p->cpus_ptr))
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continue;
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util = cpu_util_next(cpu, p, cpu);
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util = cpu_util(cpu, p, cpu);
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cpu_cap = capacity_of(cpu);
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/*
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@ -2955,53 +2955,8 @@ static inline unsigned long cpu_util_dl(struct rq *rq)
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return READ_ONCE(rq->avg_dl.util_avg);
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}
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/**
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* cpu_util_cfs() - Estimates the amount of CPU capacity used by CFS tasks.
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* @cpu: the CPU to get the utilization for.
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*
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* The unit of the return value must be the same as the one of CPU capacity
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* so that CPU utilization can be compared with CPU capacity.
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*
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* CPU utilization is the sum of running time of runnable tasks plus the
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* recent utilization of currently non-runnable tasks on that CPU.
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* It represents the amount of CPU capacity currently used by CFS tasks in
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* the range [0..max CPU capacity] with max CPU capacity being the CPU
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* capacity at f_max.
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*
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* The estimated CPU utilization is defined as the maximum between CPU
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* utilization and sum of the estimated utilization of the currently
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* runnable tasks on that CPU. It preserves a utilization "snapshot" of
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* previously-executed tasks, which helps better deduce how busy a CPU will
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* be when a long-sleeping task wakes up. The contribution to CPU utilization
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* of such a task would be significantly decayed at this point of time.
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*
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* CPU utilization can be higher than the current CPU capacity
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* (f_curr/f_max * max CPU capacity) or even the max CPU capacity because
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* of rounding errors as well as task migrations or wakeups of new tasks.
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* CPU utilization has to be capped to fit into the [0..max CPU capacity]
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* range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%)
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* could be seen as over-utilized even though CPU1 has 20% of spare CPU
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* capacity. CPU utilization is allowed to overshoot current CPU capacity
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* though since this is useful for predicting the CPU capacity required
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* after task migrations (scheduler-driven DVFS).
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*
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* Return: (Estimated) utilization for the specified CPU.
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*/
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static inline unsigned long cpu_util_cfs(int cpu)
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{
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struct cfs_rq *cfs_rq;
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unsigned long util;
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cfs_rq = &cpu_rq(cpu)->cfs;
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util = READ_ONCE(cfs_rq->avg.util_avg);
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if (sched_feat(UTIL_EST)) {
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util = max_t(unsigned long, util,
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READ_ONCE(cfs_rq->avg.util_est.enqueued));
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}
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return min(util, capacity_orig_of(cpu));
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}
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extern unsigned long cpu_util_cfs(int cpu);
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static inline unsigned long cpu_util_rt(struct rq *rq)
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{
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