linux-5.15/kswapd_try_to_sleep() の履歴(No.1)

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• linux-5.15/kswapd_try_to_sleep() へ行く。
  • 1 (2025-09-11 (木) 16:22:47)

参照元†

• linux-5.15/kswapd()

説明†

• パス: [[linux-5.15/]]

• FIXME: これは何？
  • 説明

引数†

返り値†

参考†

実装†

static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
				unsigned int highest_zoneidx)
{
	long remaining = 0;
	DEFINE_WAIT(wait);

	if (freezing(current) || kthread_should_stop())
		return;

	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);

• • linux-5.15/freezing()
  • linux-5.15/kthread_should_stop()
  • linux-5.15/prepare_to_wait()

	/*
	 * Try to sleep for a short interval. Note that kcompactd will only be
	 * woken if it is possible to sleep for a short interval. This is
	 * deliberate on the assumption that if reclaim cannot keep an
	 * eligible zone balanced that it's also unlikely that compaction will
	 * succeed.
	 */
	if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {

• • linux-5.15/prepare_kswapd_sleep()

		/*
		 * Compaction records what page blocks it recently failed to
		 * isolate pages from and skips them in the future scanning.
		 * When kswapd is going to sleep, it is reasonable to assume
		 * that pages and compaction may succeed so reset the cache.
		 */
		reset_isolation_suitable(pgdat);

• • linux-5.15/reset_isolation_suitable()

		/*
		 * We have freed the memory, now we should compact it to make
		 * allocation of the requested order possible.
		 */
		wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);

• • linux-5.15/wakeup_kcompactd()

		remaining = schedule_timeout(HZ/10);

• • linux-5.15/schedule_timeout()

		/*
		 * If woken prematurely then reset kswapd_highest_zoneidx and
		 * order. The values will either be from a wakeup request or
		 * the previous request that slept prematurely.
		 */
		if (remaining) {
			WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
					kswapd_highest_zoneidx(pgdat,
							highest_zoneidx));

			if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
				WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
		}

		finish_wait(&pgdat->kswapd_wait, &wait);
		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);

• • linux-5.15/WRITE_ONCE()
  • linux-5.15/kswapd_highest_zoneidx()
  • linux-5.15/READ_ONCE()
  • linux-5.15/finish_wait()
  • linux-5.15/prepare_to_wait()

	}

	/*
	 * After a short sleep, check if it was a premature sleep. If not, then
	 * go fully to sleep until explicitly woken up.
	 */
	if (!remaining &&
	    prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);

• • linux-5.15/prepare_kswapd_sleep()
  • linux-5.15/trace_mm_vmscan_kswapd_sleep()

		/*
		 * vmstat counters are not perfectly accurate and the estimated
		 * value for counters such as NR_FREE_PAGES can deviate from the
		 * true value by nr_online_cpus * threshold. To avoid the zone
		 * watermarks being breached while under pressure, we reduce the
		 * per-cpu vmstat threshold while kswapd is awake and restore
		 * them before going back to sleep.
		 */
		set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);

		if (!kthread_should_stop())
			schedule();

		set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);

• • linux-5.15/set_pgdat_percpu_threshold()
  • linux-5.15/kthread_should_stop()

	} else {
		if (remaining)
			count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
		else
			count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
	}
	finish_wait(&pgdat->kswapd_wait, &wait);
}

• • linux-5.15/count_vm_event()
  • linux-5.15/finish_wait()

コメント†