Messages in this thread Patch in this message | | | From | Dietmar Eggemann <> | Subject | [PATCH] sched/fair: Replace CFS internal cpu_util() with cpu_util_cfs() | Date | Fri, 12 Nov 2021 15:13:49 +0100 |
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cpu_util_cfs() was created by commit d4edd662ac16 ("sched/cpufreq: Use the DEADLINE utilization signal") to enable the access to CPU utilization from the Schedutil CPUfreq governor.
Commit a07630b8b2c1 ("sched/cpufreq/schedutil: Use util_est for OPP selection") added util_est support later.
The only thing cpu_util() is doing on top of what cpu_util_cfs() already does is to clamp the return value to the [0..capacity_orig] capacity range of the CPU. Integrating this into cpu_util_cfs() is not harming the existing users (Schedutil and CPUfreq cooling (latter via sched_cpu_util() wrapper)).
Remove cpu_util().
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> ---
I deliberately got rid of the comment on top of cpu_util(). It's from the early days of using PELT utilization, it describes CPU utilization behaviour before PELT time-scaling and talks about current capacity which we don't maintain.
kernel/sched/fair.c | 65 ++++---------------------------------------- kernel/sched/sched.h | 2 +- 2 files changed, 6 insertions(+), 61 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 13950beb01a2..7a815b10c0c3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1502,7 +1502,6 @@ struct task_numa_env { static unsigned long cpu_load(struct rq *rq); static unsigned long cpu_runnable(struct rq *rq); -static unsigned long cpu_util(int cpu); static inline long adjust_numa_imbalance(int imbalance, int dst_running, int dst_weight); @@ -1569,7 +1568,7 @@ static void update_numa_stats(struct task_numa_env *env, ns->load += cpu_load(rq); ns->runnable += cpu_runnable(rq); - ns->util += cpu_util(cpu); + ns->util += cpu_util_cfs(rq); ns->nr_running += rq->cfs.h_nr_running; ns->compute_capacity += capacity_of(cpu); @@ -5509,11 +5508,9 @@ static inline void hrtick_update(struct rq *rq) #endif #ifdef CONFIG_SMP -static inline unsigned long cpu_util(int cpu); - static inline bool cpu_overutilized(int cpu) { - return !fits_capacity(cpu_util(cpu), capacity_of(cpu)); + return !fits_capacity(cpu_util_cfs(cpu_rq(cpu)), capacity_of(cpu)); } static inline void update_overutilized_status(struct rq *rq) @@ -6456,58 +6453,6 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) return target; } -/** - * cpu_util - Estimates the amount of capacity of a CPU used by CFS tasks. - * @cpu: the CPU to get the utilization of - * - * The unit of the return value must be the one of capacity so we can compare - * the utilization with the capacity of the CPU that is available for CFS task - * (ie cpu_capacity). - * - * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the - * recent utilization of currently non-runnable tasks on a CPU. It represents - * the amount of utilization of a CPU in the range [0..capacity_orig] where - * capacity_orig is the cpu_capacity available at the highest frequency - * (arch_scale_freq_capacity()). - * The utilization of a CPU converges towards a sum equal to or less than the - * current capacity (capacity_curr <= capacity_orig) of the CPU because it is - * the running time on this CPU scaled by capacity_curr. - * - * The estimated utilization of a CPU is defined to be the maximum between its - * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks - * currently RUNNABLE on that CPU. - * This allows to properly represent the expected utilization of a CPU which - * has just got a big task running since a long sleep period. At the same time - * however it preserves the benefits of the "blocked utilization" in - * describing the potential for other tasks waking up on the same CPU. - * - * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even - * higher than capacity_orig because of unfortunate rounding in - * cfs.avg.util_avg or just after migrating tasks and new task wakeups until - * the average stabilizes with the new running time. We need to check that the - * utilization stays within the range of [0..capacity_orig] and cap it if - * necessary. Without utilization capping, a group could be seen as overloaded - * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of - * available capacity. We allow utilization to overshoot capacity_curr (but not - * capacity_orig) as it useful for predicting the capacity required after task - * migrations (scheduler-driven DVFS). - * - * Return: the (estimated) utilization for the specified CPU - */ -static inline unsigned long cpu_util(int cpu) -{ - struct cfs_rq *cfs_rq; - unsigned int util; - - cfs_rq = &cpu_rq(cpu)->cfs; - util = READ_ONCE(cfs_rq->avg.util_avg); - - if (sched_feat(UTIL_EST)) - util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued)); - - return min_t(unsigned long, util, capacity_orig_of(cpu)); -} - /* * cpu_util_without: compute cpu utilization without any contributions from *p * @cpu: the CPU which utilization is requested @@ -6528,7 +6473,7 @@ static unsigned long cpu_util_without(int cpu, struct task_struct *p) /* Task has no contribution or is new */ if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) - return cpu_util(cpu); + return cpu_util_cfs(cpu_rq(cpu)); cfs_rq = &cpu_rq(cpu)->cfs; util = READ_ONCE(cfs_rq->avg.util_avg); @@ -8681,7 +8626,7 @@ static inline void update_sg_lb_stats(struct lb_env *env, struct rq *rq = cpu_rq(i); sgs->group_load += cpu_load(rq); - sgs->group_util += cpu_util(i); + sgs->group_util += cpu_util_cfs(rq); sgs->group_runnable += cpu_runnable(rq); sgs->sum_h_nr_running += rq->cfs.h_nr_running; @@ -9699,7 +9644,7 @@ static struct rq *find_busiest_queue(struct lb_env *env, break; case migrate_util: - util = cpu_util(cpu_of(rq)); + util = cpu_util_cfs(rq); /* * Don't try to pull utilization from a CPU with one diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index f0b249ec581d..d49eda251049 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2951,7 +2951,7 @@ static inline unsigned long cpu_util_cfs(struct rq *rq) READ_ONCE(rq->cfs.avg.util_est.enqueued)); } - return util; + return min(util, capacity_orig_of(cpu_of(rq))); } static inline unsigned long cpu_util_rt(struct rq *rq) -- 2.25.1
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