linux-5.15/kcompactd() の履歴(No.1)

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• linux-5.15/kcompactd() へ行く。
  • 1 (2025-09-11 (木) 13:44:47)

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説明†

• パス: [[linux-5.15/]]

• FIXME: これは何？
  • 説明

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返り値†

参考†

実装†

/*
 * The background compaction daemon, started as a kernel thread
 * from the init process.
 */
static int kcompactd(void *p)
{
	pg_data_t *pgdat = (pg_data_t *)p;
	struct task_struct *tsk = current;
	long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
	long timeout = default_timeout;

	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);

	if (!cpumask_empty(cpumask))
		set_cpus_allowed_ptr(tsk, cpumask);

	set_freezable();

• • linux-5.15/pg_data_t
  • linux-5.15/task_struct
  • linux-5.15/msecs_to_jiffies()
  • linux-5.15/cpumask
  • linux-5.15/cpumask_of_node()
  • linux-5.15/cpumask_empty()
  • linux-5.15/set_cpus_allowed_ptr()
  • linux-5.15/set_freezable()

	pgdat->kcompactd_max_order = 0;
	pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1;

	while (!kthread_should_stop()) {
		unsigned long pflags;

		/*
		 * Avoid the unnecessary wakeup for proactive compaction
		 * when it is disabled.
		 */
		if (!sysctl_compaction_proactiveness)
			timeout = MAX_SCHEDULE_TIMEOUT;
		trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
		if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
			kcompactd_work_requested(pgdat), timeout) &&
			!pgdat->proactive_compact_trigger) {

• • linux-5.15/kthread_should_stop()
  • linux-5.15/trace_mm_compaction_kcompactd_sleep()
  • linux-5.15/wait_freezable_timeout()
  • linux-5.15/kcompactd_work_requested()

			psi_memstall_enter(&pflags);
			kcompactd_do_work(pgdat);
			psi_memstall_leave(&pflags);
			/*
			 * Reset the timeout value. The defer timeout from
			 * proactive compaction is lost here but that is fine
			 * as the condition of the zone changing substantionally
			 * then carrying on with the previous defer interval is
			 * not useful.
			 */
			timeout = default_timeout;
			continue;
		}

• • linux-5.15/psi_memstall_enter()
  • linux-5.15/kcompactd_do_work()
  • linux-5.15/psi_memstall_leave()

		/*
		 * Start the proactive work with default timeout. Based
		 * on the fragmentation score, this timeout is updated.
		 */
		timeout = default_timeout;
		if (should_proactive_compact_node(pgdat)) {
			unsigned int prev_score, score;

			prev_score = fragmentation_score_node(pgdat);
			proactive_compact_node(pgdat);
			score = fragmentation_score_node(pgdat);
			/*
			 * Defer proactive compaction if the fragmentation
			 * score did not go down i.e. no progress made.
			 */
			if (unlikely(score >= prev_score))
				timeout =
				   default_timeout << COMPACT_MAX_DEFER_SHIFT;
		}
		if (unlikely(pgdat->proactive_compact_trigger))
			pgdat->proactive_compact_trigger = false;

• • linux-5.15/should_proactive_compact_node()
  • linux-5.15/fragmentation_score_node()
  • linux-5.15/proactive_compact_node()
  • linux-5.15/unlikely()

	}

	return 0;
}

• • [[linux-5.15/]]

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