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

• 履歴一覧
• 差分 を表示
• 現在との差分 を表示
• ソース を表示
• linux-5.15/__rmqueue_fallback() へ行く。
  • 1 (2025-09-13 (土) 02:10:25)

参照元†

• linux-5.15/__rmqueue()

説明†

• パス: linux-5.15/mm/page_alloc.c

• FIXME: これは何？
  • 説明

引数†

• struct zone *zone
  • linux-5.15/zone
  • int order
  • int start_migratetype
  • unsigned int alloc_flags

返り値†

• bool

参考†

実装†

/*
 * Try finding a free buddy page on the fallback list and put it on the free
 * list of requested migratetype, possibly along with other pages from the same
 * block, depending on fragmentation avoidance heuristics. Returns true if
 * fallback was found so that __rmqueue_smallest() can grab it.
 *
 * The use of signed ints for order and current_order is a deliberate
 * deviation from the rest of this file, to make the for loop
 * condition simpler.
 */
static __always_inline bool
__rmqueue_fallback(struct zone *zone, int order, int start_migratetype,
						unsigned int alloc_flags)
{
	struct free_area *area;
	int current_order;
	int min_order = order;
	struct page *page;
	int fallback_mt;
	bool can_steal;

	/*
	 * Do not steal pages from freelists belonging to other pageblocks
	 * i.e. orders < pageblock_order. If there are no local zones free,
	 * the zonelists will be reiterated without ALLOC_NOFRAGMENT.
	 */
	if (alloc_flags & ALLOC_NOFRAGMENT)
		min_order = pageblock_order;

• • linux-5.15/free_area
  • linux-5.15/page

	/*
	 * Find the largest available free page in the other list. This roughly
	 * approximates finding the pageblock with the most free pages, which
	 * would be too costly to do exactly.
	 */
	for (current_order = MAX_ORDER - 1; current_order >= min_order;
				--current_order) {
		area = &(zone->free_area[current_order]);
		fallback_mt = find_suitable_fallback(area, current_order,
				start_migratetype, false, &can_steal);
		if (fallback_mt == -1)
			continue;

		/*
		 * We cannot steal all free pages from the pageblock and the
		 * requested migratetype is movable. In that case it's better to
		 * steal and split the smallest available page instead of the
		 * largest available page, because even if the next movable
		 * allocation falls back into a different pageblock than this
		 * one, it won't cause permanent fragmentation.
		 */
		if (!can_steal && start_migratetype == MIGRATE_MOVABLE
					&& current_order > order)
			goto find_smallest;

		goto do_steal;
	}

	return false;

• • linux-5.15/find_suitable_fallback()

find_smallest:
	for (current_order = order; current_order < MAX_ORDER;
							current_order++) {
		area = &(zone->free_area[current_order]);
		fallback_mt = find_suitable_fallback(area, current_order,
				start_migratetype, false, &can_steal);
		if (fallback_mt != -1)
			break;
	}

	/*
	 * This should not happen - we already found a suitable fallback
	 * when looking for the largest page.
	 */
	VM_BUG_ON(current_order == MAX_ORDER);

• • linux-5.15/find_suitable_fallback()
  • linux-5.15/VM_BUG_ON()

do_steal:
	page = get_page_from_free_area(area, fallback_mt);

	steal_suitable_fallback(zone, page, alloc_flags, start_migratetype,
								can_steal);

	trace_mm_page_alloc_extfrag(page, order, current_order,
		start_migratetype, fallback_mt);

	return true;

}

• • linux-5.15/get_page_from_free_area()
  • linux-5.15/steal_suitable_fallback()
  • linux-5.15/trace_mm_page_alloc_extfrag()

コメント†