Commit 28073b02 authored by Hillf Danton's avatar Hillf Danton Committed by Linus Torvalds
Browse files

mm: hugetlb: defer freeing pages when gathering surplus pages 



When gathering surplus pages, the number of needed pages is recomputed
after reacquiring hugetlb lock to catch changes in resv_huge_pages and
free_huge_pages.  Plus it is recomputed with the number of newly allocated
pages involved.

Thus freeing pages can be deferred a bit to see if the final page request
is satisfied, though pages could be allocated less than needed.

Signed-off-by: default avatarHillf Danton <dhillf@gmail.com>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cc715d99

mm/hugetlb.c

+17 −13
Original line number Diff line number Diff line
@@ -852,6 +852,7 @@ static int gather_surplus_pages(struct hstate *h, int delta) 
	struct page *page, *tmp;

	int ret, i;

	int needed, allocated;

	bool alloc_ok = true;



	needed = (h->resv_huge_pages + delta) - h->free_huge_pages;

	if (needed <= 0) {
@@ -867,17 +868,13 @@ retry: 
	spin_unlock(&hugetlb_lock);

	for (i = 0; i < needed; i++) {

		page = alloc_buddy_huge_page(h, NUMA_NO_NODE);

		if (!page)

			/*

			 * We were not able to allocate enough pages to

			 * satisfy the entire reservation so we free what

			 * we've allocated so far.

			 */

			goto free;



		if (!page) {

			alloc_ok = false;

			break;

		}

		list_add(&page->lru, &surplus_list);

	}

	allocated += needed;

	allocated += i;



	/*

	 * After retaking hugetlb_lock, we need to recalculate 'needed'
@@ -886,9 +883,16 @@ retry: 
	spin_lock(&hugetlb_lock);

	needed = (h->resv_huge_pages + delta) -

			(h->free_huge_pages + allocated);

	if (needed > 0)

	if (needed > 0) {

		if (alloc_ok)

			goto retry;



		/*

		 * We were not able to allocate enough pages to

		 * satisfy the entire reservation so we free what

		 * we've allocated so far.

		 */

		goto free;

	}

	/*

	 * The surplus_list now contains _at_least_ the number of extra pages

	 * needed to accommodate the reservation.  Add the appropriate number
@@ -914,10 +918,10 @@ retry: 
		VM_BUG_ON(page_count(page));

		enqueue_huge_page(h, page);

	}

free:

	spin_unlock(&hugetlb_lock);



	/* Free unnecessary surplus pages to the buddy allocator */

free:

	if (!list_empty(&surplus_list)) {

		list_for_each_entry_safe(page, tmp, &surplus_list, lru) {

			list_del(&page->lru);

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