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Commit 86a4ac43 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull scheduler fix from Thomas Gleixner:
 "Revert the new NUMA aware placement approach which turned out to
  create more problems than it solved"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "sched/numa: Delay retrying placement for automatic NUMA balance after wake_affine()"
parents baeda713 789ba280

kernel/sched/fair.c

+1 −56
Original line number Diff line number Diff line
@@ -1854,7 +1854,6 @@ static int task_numa_migrate(struct task_struct *p) 
static void numa_migrate_preferred(struct task_struct *p)

{

	unsigned long interval = HZ;

	unsigned long numa_migrate_retry;



	/* This task has no NUMA fault statistics yet */

	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
@@ -1862,18 +1861,7 @@ static void numa_migrate_preferred(struct task_struct *p) 


	/* Periodically retry migrating the task to the preferred node */

	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);

	numa_migrate_retry = jiffies + interval;



	/*

	 * Check that the new retry threshold is after the current one. If

	 * the retry is in the future, it implies that wake_affine has

	 * temporarily asked NUMA balancing to backoff from placement.

	 */

	if (numa_migrate_retry > p->numa_migrate_retry)

		return;



	/* Safe to try placing the task on the preferred node */

	p->numa_migrate_retry = numa_migrate_retry;

	p->numa_migrate_retry = jiffies + interval;



	/* Success if task is already running on preferred CPU */

	if (task_node(p) == p->numa_preferred_nid)
@@ -5922,48 +5910,6 @@ wake_affine_weight(struct sched_domain *sd, struct task_struct *p, 
	return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;

}



#ifdef CONFIG_NUMA_BALANCING

static void

update_wa_numa_placement(struct task_struct *p, int prev_cpu, int target)

{

	unsigned long interval;



	if (!static_branch_likely(&sched_numa_balancing))

		return;



	/* If balancing has no preference then continue gathering data */

	if (p->numa_preferred_nid == -1)

		return;



	/*

	 * If the wakeup is not affecting locality then it is neutral from

	 * the perspective of NUMA balacing so continue gathering data.

	 */

	if (cpu_to_node(prev_cpu) == cpu_to_node(target))

		return;



	/*

	 * Temporarily prevent NUMA balancing trying to place waker/wakee after

	 * wakee has been moved by wake_affine. This will potentially allow

	 * related tasks to converge and update their data placement. The

	 * 4 * numa_scan_period is to allow the two-pass filter to migrate

	 * hot data to the wakers node.

	 */

	interval = max(sysctl_numa_balancing_scan_delay,

			 p->numa_scan_period << 2);

	p->numa_migrate_retry = jiffies + msecs_to_jiffies(interval);



	interval = max(sysctl_numa_balancing_scan_delay,

			 current->numa_scan_period << 2);

	current->numa_migrate_retry = jiffies + msecs_to_jiffies(interval);

}

#else

static void

update_wa_numa_placement(struct task_struct *p, int prev_cpu, int target)

{

}

#endif



static int wake_affine(struct sched_domain *sd, struct task_struct *p,

		       int this_cpu, int prev_cpu, int sync)

{
@@ -5979,7 +5925,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, 
	if (target == nr_cpumask_bits)

		return prev_cpu;



	update_wa_numa_placement(p, prev_cpu, target);

	schedstat_inc(sd->ttwu_move_affine);

	schedstat_inc(p->se.statistics.nr_wakeups_affine);

	return target;