함수 선언

https://elixir.bootlin.com/linux/v6.10.3/source/kernel/sched/sched.h#L1795 extern void [**init_numa_balancing**](<https://elixir.bootlin.com/linux/v6.10.3/C/ident/init_numa_balancing>)(unsigned long [**clone_flags**](<https://elixir.bootlin.com/linux/v6.10.3/C/ident/clone_flags>), struct [**task_struct**](<https://elixir.bootlin.com/linux/v6.10.3/C/ident/task_struct>) *p);

함수 정의

https://elixir.bootlin.com/linux/v6.10.3/source/kernel/sched/fair.c#L3442

void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
{
	int mm_users = 0;
	struct mm_struct *mm = p->mm;

	if (mm) {
		mm_users = atomic_read(&mm->mm_users);
		if (mm_users == 1) {
			mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
			mm->numa_scan_seq = 0;
		}
	}
	p->node_stamp			= 0;
	p->numa_scan_seq		= mm ? mm->numa_scan_seq : 0;
	p->numa_scan_period		= sysctl_numa_balancing_scan_delay;
	p->numa_migrate_retry		= 0;
	/* Protect against double add, see task_tick_numa and task_numa_work */
	p->numa_work.next		= &p->numa_work;
	p->numa_faults			= NULL;
	p->numa_pages_migrated		= 0;
	p->total_numa_faults		= 0;
	RCU_INIT_POINTER(p->numa_group, NULL);
	p->last_task_numa_placement	= 0;
	p->last_sum_exec_runtime	= 0;

	init_task_work(&p->numa_work, task_numa_work);

	/* New address space, reset the preferred nid */
	if (!(clone_flags & CLONE_VM)) {
		p->numa_preferred_nid = NUMA_NO_NODE;
		return;
	}

	/*
	 * New thread, keep existing numa_preferred_nid which should be copied
	 * already by arch_dup_task_struct but stagger when scans start.
	 */
	if (mm) {
		unsigned int delay;

		delay = min_t(unsigned int, task_scan_max(current),
			current->numa_scan_period * mm_users * NSEC_PER_MSEC);
		delay += 2 * TICK_NSEC;
		p->node_stamp = delay;
	}
}

함수 역할

• numa scan과 관련 파라미터를 초기화한다.
  • NUMA scan은 새 태스크가 생성될 때 마다 실행됨
• kernel/sched/fair.c에 위치
  • NUMA Balancing과 관련된 코드들이 모여있는 곳

언제 호출되는가?

새 프로세스를 만들 때, 즉 fork가 일어날 때 일어난다.

callstack

• copy_process() -> sched_fork() ->  __sched_fork() -> init_numa_balancing()

출처 : http://www.iamroot.org/xe/index.php?mid=Note&document_srl=220522

파라미터

init_numa_balancing(unsigned long clone_flags, struct task_struct *p)

unsigned long clone_flags : _do_fork() 호출 시 전달되는 인자1가 여기에도 전달