linux-5.15/steal_suitable_fallback() の変更点

• 追加された行はこの色です。
• 削除された行はこの色です。
• linux-5.15/steal_suitable_fallback() へ行く。
• linux-5.15/steal_suitable_fallback() の差分を削除

#author("2025-09-13T02:14:27+09:00","default:guest","guest")

*参照元 [#qea971d4]
#backlinks

*説明 [#ea83ae9b]
-パス: [[linux-5.15/mm/page_alloc.c]]

-FIXME: これは何？
--説明


**引数 [#jdb7bf89]
-struct zone *zone
--
--[[linux-5.15/zone]]
-struct page *page
--
--[[linux-5.15/page]]
-unsigned int alloc_flags
--
-int start_type
--
-bool whole_block
--


**返り値 [#sd84f815]
-なし


**参考 [#t6284162]


*実装 [#g72c5483]

 /*
  * This function implements actual steal behaviour. If order is large enough,
  * we can steal whole pageblock. If not, we first move freepages in this
  * pageblock to our migratetype and determine how many already-allocated pages
  * are there in the pageblock with a compatible migratetype. If at least half
  * of pages are free or compatible, we can change migratetype of the pageblock
  * itself, so pages freed in the future will be put on the correct free list.
  */
 static void steal_suitable_fallback(struct zone *zone, struct page *page,
 		unsigned int alloc_flags, int start_type, bool whole_block)
 {
 	unsigned int current_order = buddy_order(page);
 	int free_pages, movable_pages, alike_pages;
 	int old_block_type;
 
 	old_block_type = get_pageblock_migratetype(page);
 
-
--[[linux-5.15/buddy_order()]]
--[[linux-5.15/get_pageblock_migratetype()]]

 	/*
 	 * This can happen due to races and we want to prevent broken
 	 * highatomic accounting.
 	 */
 	if (is_migrate_highatomic(old_block_type))
 		goto single_page;
 
-
--[[linux-5.15/is_migrate_highatomic()]]

 	/* Take ownership for orders >= pageblock_order */
 	if (current_order >= pageblock_order) {
 		change_pageblock_range(page, current_order, start_type);
 		goto single_page;
 	}
 
-
--[[linux-5.15/change_pageblock_range()]]

 	/*
 	 * Boost watermarks to increase reclaim pressure to reduce the
 	 * likelihood of future fallbacks. Wake kswapd now as the node
 	 * may be balanced overall and kswapd will not wake naturally.
 	 */
 	if (boost_watermark(zone) && (alloc_flags & ALLOC_KSWAPD))
 		set_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
 
-
--[[linux-5.15/boost_watermark()]]
--[[linux-5.15/set_bit()]]

 	/* We are not allowed to try stealing from the whole block */
 	if (!whole_block)
 		goto single_page;
 
 	free_pages = move_freepages_block(zone, page, start_type,
 						&movable_pages);
-
--[[linux-5.15/move_freepages_block()]]

 	/*
 	 * Determine how many pages are compatible with our allocation.
 	 * For movable allocation, it's the number of movable pages which
 	 * we just obtained. For other types it's a bit more tricky.
 	 */
 	if (start_type == MIGRATE_MOVABLE) {
 		alike_pages = movable_pages;
 	} else {
 		/*
 		 * If we are falling back a RECLAIMABLE or UNMOVABLE allocation
 		 * to MOVABLE pageblock, consider all non-movable pages as
 		 * compatible. If it's UNMOVABLE falling back to RECLAIMABLE or
 		 * vice versa, be conservative since we can't distinguish the
 		 * exact migratetype of non-movable pages.
 		 */
 		if (old_block_type == MIGRATE_MOVABLE)
 			alike_pages = pageblock_nr_pages
 						- (free_pages + movable_pages);
 		else
 			alike_pages = 0;
 	}
 
 	/* moving whole block can fail due to zone boundary conditions */
 	if (!free_pages)
 		goto single_page;
 
 	/*
 	 * If a sufficient number of pages in the block are either free or of
 	 * comparable migratability as our allocation, claim the whole block.
 	 */
 	if (free_pages + alike_pages >= (1 << (pageblock_order-1)) ||
 			page_group_by_mobility_disabled)
 		set_pageblock_migratetype(page, start_type);
 
 	return;
 
-
--[[linux-5.15/set_pageblock_migratetype()]]

 single_page:
 	move_to_free_list(page, zone, current_order, start_type);
 }

-
--[[linux-5.15/move_to_free_list()]]


*コメント [#o725d1ab]