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: Hillf Danton <dhillf@gmail.com>
Reviewed-by: Michal 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a876871..afe3e1f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -852,6 +852,7 @@
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 @@
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 @@
spin_lock(&hugetlb_lock);
needed = (h->resv_huge_pages + delta) -
(h->free_huge_pages + allocated);
- if (needed > 0)
- goto retry;
-
+ 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 @@
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);