mm: reduce the amount of work done when updating min_free_kbytes (938929f1) · Commits · 戴 / test

When min_free_kbytes is updated, some pageblocks are marked MIGRATE_RESERVE. Ordinarily, this work is unnoticable as it happens early in boot but on large machines with 1TB of memory, this has been reported to delay boot times, probably due to the NUMA distances involved. The bulk of the work is due to calling calling pageblock_is_reserved() an unnecessary amount of times and accessing far more struct page metadata than is necessary. This patch significantly reduces the amount of work done by setup_zone_migrate_reserve() improving boot times on 1TB machines. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by:

Mel Gorman <mgorman@suse.de> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

+24 −16

Original line number	Diff line number	Diff line
		@@ -3388,26 +3388,34 @@ static void setup_zone_migrate_reserve(struct zone *zone)
		if (page_to_nid(page) != zone_to_nid(zone))
		continue;

		/* Blocks with reserved pages will never free, skip them. */
		block_migratetype = get_pageblock_migratetype(page);

		/* Only test what is necessary when the reserves are not met */
		if (reserve > 0) {
		/*
		* Blocks with reserved pages will never free, skip
		* them.
		*/
		block_end_pfn = min(pfn + pageblock_nr_pages, end_pfn);
		if (pageblock_is_reserved(pfn, block_end_pfn))
		continue;

		block_migratetype = get_pageblock_migratetype(page);

		/* If this block is reserved, account for it */
		if (reserve > 0 && block_migratetype == MIGRATE_RESERVE) {
		if (block_migratetype == MIGRATE_RESERVE) {
		reserve--;
		continue;
		}

		/* Suitable for reserving if this block is movable */
		if (reserve > 0 && block_migratetype == MIGRATE_MOVABLE) {
		set_pageblock_migratetype(page, MIGRATE_RESERVE);
		move_freepages_block(zone, page, MIGRATE_RESERVE);
		if (block_migratetype == MIGRATE_MOVABLE) {
		set_pageblock_migratetype(page,
		MIGRATE_RESERVE);
		move_freepages_block(zone, page,
		MIGRATE_RESERVE);
		reserve--;
		continue;
		}
		}

		/*
		* If the reserve is met and this is a previous reserved block,

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