sched/fair: Add comments for group_type and balancing at SD_NUMA level (a9723389) · Commits · 戴 / test

kernel/sched/fair.c

+31 −4

Original line number	Diff line number	Diff line
		@@ -6980,17 +6980,40 @@ static unsigned long __read_mostly max_load_balance_interval = HZ/10;
		enum fbq_type { regular, remote, all };

		/*
		* group_type describes the group of CPUs at the moment of the load balance.
		* 'group_type' describes the group of CPUs at the moment of load balancing.
		*
		* The enum is ordered by pulling priority, with the group with lowest priority
		* first so the groupe_type can be simply compared when selecting the busiest
		* group. see update_sd_pick_busiest().
		* first so the group_type can simply be compared when selecting the busiest
		* group. See update_sd_pick_busiest().
		*/
		enum group_type {
		/* The group has spare capacity that can be used to run more tasks. */
		group_has_spare = 0,
		/*
		* The group is fully used and the tasks don't compete for more CPU
		* cycles. Nevertheless, some tasks might wait before running.
		*/
		group_fully_busy,
		/*
		* SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity
		* and must be migrated to a more powerful CPU.
		*/
		group_misfit_task,
		/*
		* SD_ASYM_PACKING only: One local CPU with higher capacity is available,
		* and the task should be migrated to it instead of running on the
		* current CPU.
		*/
		group_asym_packing,
		/*
		* The tasks' affinity constraints previously prevented the scheduler
		* from balancing the load across the system.
		*/
		group_imbalanced,
		/*
		* The CPU is overloaded and can't provide expected CPU cycles to all
		* tasks.
		*/
		group_overloaded
		};

		@@ -8589,7 +8612,11 @@ static inline void calculate_imbalance(struct lb_env env, struct sd_lb_stats s

		/*
		* Try to use spare capacity of local group without overloading it or
		* emptying busiest
		* emptying busiest.
		* XXX Spreading tasks across NUMA nodes is not always the best policy
		* and special care should be taken for SD_NUMA domain level before
		* spreading the tasks. For now, load_balance() fully relies on
		* NUMA_BALANCING and fbq_classify_group/rq to override the decision.
		*/
		if (local->group_type == group_has_spare) {
		if (busiest->group_type > group_fully_busy) {

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