Commit 745fcb6d authored Jun 27, 2024 by Zhang Qiao Committed by Zheng Zengkai Jun 27, 2024

sched/numa: Fix numa imbalance in load_balance()

hulk inclusion
category: performance
bugzilla: https://gitee.com/openeuler/kernel/issues/I9RMHW


CVE: NA

--------------------------------

When perform load balance, a NUMA imbalance is allowed
if busy CPUs is less than the maximum threshold, it
keeps a pair of communication tasks on the current
node when the destination is lightly loaded.

1. But, calculate_imbalance() use local->sum_nr_running,
it may not be accurate, because communication tasks is
on busiest group, so should be busiest->sum_nr_running.

2. At the same time, idles cpus are used to calculate
imbalance, but the group_weight may not be the same
between local and busiest groups. In this case, even if
both groups are very idle, imbalance will be calculated
very large, so the imbalance is calculated by calculating
the difference of busy cpus between groups.

Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>

Conflicts:
	kernel/sched/fair.c
Signed-off-by: Zhao Wenhui <zhaowenhui8@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>

parent 34f4979f

kernel/sched/fair.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -11465,17 +11465,19 @@ static inline void calculate_imbalance(struct lb_env env, struct sd_lb_stats s

		/*
		* If there is no overload, we just want to even the number of
		* idle cpus.
		* busy cpus.
		*/
		env->migration_type = migrate_task;
		env->imbalance = max_t(long, 0, (local->idle_cpus -
		busiest->idle_cpus) >> 1);
		env->imbalance = max_t(long, 0,
		((busiest->group_weight - busiest->idle_cpus)
		- (local->group_weight - local->idle_cpus)) >> 1);
		}

		/* Consider allowing a small imbalance between NUMA groups */
		if (env->sd->flags & SD_NUMA) {
		env->imbalance = adjust_numa_imbalance(env->imbalance,
		local->sum_nr_running + 1, env->sd->imb_numa_nr);
		busiest->sum_nr_running,
		env->sd->imb_numa_nr);
		}

		return;