hugetlb: use free_pool_huge_page() to return unused surplus pages

Use the [modified] free_pool_huge_page() function to return unused
surplus pages.  This will help keep huge pages balanced across nodes
between freeing of unused surplus pages and freeing of persistent huge
pages [from set_max_huge_pages] by using the same node id "cursor". It
also eliminates some code duplication.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Eric Whitney <eric.whitney@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 24 insertions, 33 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 38dab5586827..f10cc274a7d9 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -687,7 +687,7 @@ static int hstate_next_node_to_free(struct hstate *h)
  * balanced over allowed nodes.
  * Called with hugetlb_lock locked.
  */
-static int free_pool_huge_page(struct hstate *h)
+static int free_pool_huge_page(struct hstate *h, bool acct_surplus)
 {
         int start_nid;
         int next_nid;
@@ -697,13 +697,22 @@ static int free_pool_huge_page(struct hstate *h)
         next_nid = start_nid;
 
         do {
-                if (!list_empty(&h->hugepage_freelists[next_nid])) {
+                /*
+                 * If we're returning unused surplus pages, only examine
+                 * nodes with surplus pages.
+                 */
+                if ((!acct_surplus || h->surplus_huge_pages_node[next_nid]) &&
+                    !list_empty(&h->hugepage_freelists[next_nid])) {
                         struct page *page =
                                 list_entry(h->hugepage_freelists[next_nid].next,
                                           struct page, lru);
                         list_del(&page->lru);
                         h->free_huge_pages--;
                         h->free_huge_pages_node[next_nid]--;
+                        if (acct_surplus) {
+                                h->surplus_huge_pages--;
+                                h->surplus_huge_pages_node[next_nid]--;
+                        }
                         update_and_free_page(h, page);
                         ret = 1;
                 }
@@ -884,22 +893,13 @@ free:
  * When releasing a hugetlb pool reservation, any surplus pages that were
  * allocated to satisfy the reservation must be explicitly freed if they were
  * never used.
+ * Called with hugetlb_lock held.
  */
 static void return_unused_surplus_pages(struct hstate *h,
                                         unsigned long unused_resv_pages)
 {
-        static int nid = -1;
-        struct page *page;
         unsigned long nr_pages;
 
-        /*
-         * We want to release as many surplus pages as possible, spread
-         * evenly across all nodes. Iterate across all nodes until we
-         * can no longer free unreserved surplus pages. This occurs when
-         * the nodes with surplus pages have no free pages.
-         */
-        unsigned long remaining_iterations = nr_online_nodes;
-
         /* Uncommit the reservation */
         h->resv_huge_pages -= unused_resv_pages;
 
@@ -909,26 +909,17 @@ static void return_unused_surplus_pages(struct hstate *h,
 
         nr_pages = min(unused_resv_pages, h->surplus_huge_pages);
 
-        while (remaining_iterations-- && nr_pages) {
-                nid = next_node(nid, node_online_map);
-                if (nid == MAX_NUMNODES)
-                        nid = first_node(node_online_map);
-
-                if (!h->surplus_huge_pages_node[nid])
-                        continue;
-
-                if (!list_empty(&h->hugepage_freelists[nid])) {
-                        page = list_entry(h->hugepage_freelists[nid].next,
-                                          struct page, lru);
-                        list_del(&page->lru);
-                        update_and_free_page(h, page);
-                        h->free_huge_pages--;
-                        h->free_huge_pages_node[nid]--;
-                        h->surplus_huge_pages--;
-                        h->surplus_huge_pages_node[nid]--;
-                        nr_pages--;
-                        remaining_iterations = nr_online_nodes;
-                }
+        /*
+         * We want to release as many surplus pages as possible, spread
+         * evenly across all nodes. Iterate across all nodes until we
+         * can no longer free unreserved surplus pages. This occurs when
+         * the nodes with surplus pages have no free pages.
+         * free_pool_huge_page() will balance the the frees across the
+         * on-line nodes for us and will handle the hstate accounting.
+         */
+        while (nr_pages--) {
+                if (!free_pool_huge_page(h, 1))
+                        break;
         }
 }
 
@@ -1268,7 +1259,7 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count)
         min_count = max(count, min_count);
         try_to_free_low(h, min_count);
         while (min_count < persistent_huge_pages(h)) {
-                if (!free_pool_huge_page(h))
+                if (!free_pool_huge_page(h, 0))
                         break;
         }
         while (count < persistent_huge_pages(h)) {