diff mbox series

[043/143] hugetlb: call update_and_free_page without hugetlb_lock

Message ID 20210505013459.leKF4uKLC%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [001/143] mm: introduce and use mapping_empty() | expand

Commit Message

Andrew Morton May 5, 2021, 1:34 a.m. UTC
From: Mike Kravetz <mike.kravetz@oracle.com>
Subject: hugetlb: call update_and_free_page without hugetlb_lock

With the introduction of remove_hugetlb_page(), there is no need for
update_and_free_page to hold the hugetlb lock.  Change all callers to drop
the lock before calling.

With additional code modifications, this will allow loops which decrease
the huge page pool to drop the hugetlb_lock with each page to reduce long
hold times.

The ugly unlock/lock cycle in free_pool_huge_page will be removed in a
subsequent patch which restructures free_pool_huge_page.

Link: https://lkml.kernel.org/r/20210409205254.242291-6-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |   31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)
diff mbox series

Patch

--- a/mm/hugetlb.c~hugetlb-call-update_and_free_page-without-hugetlb_lock
+++ a/mm/hugetlb.c
@@ -1451,16 +1451,18 @@  static void __free_huge_page(struct page
 
 	if (HPageTemporary(page)) {
 		remove_hugetlb_page(h, page, false);
+		spin_unlock(&hugetlb_lock);
 		update_and_free_page(h, page);
 	} else if (h->surplus_huge_pages_node[nid]) {
 		/* remove the page from active list */
 		remove_hugetlb_page(h, page, true);
+		spin_unlock(&hugetlb_lock);
 		update_and_free_page(h, page);
 	} else {
 		arch_clear_hugepage_flags(page);
 		enqueue_huge_page(h, page);
+		spin_unlock(&hugetlb_lock);
 	}
-	spin_unlock(&hugetlb_lock);
 }
 
 /*
@@ -1741,7 +1743,13 @@  static int free_pool_huge_page(struct hs
 				list_entry(h->hugepage_freelists[node].next,
 					  struct page, lru);
 			remove_hugetlb_page(h, page, acct_surplus);
+			/*
+			 * unlock/lock around update_and_free_page is temporary
+			 * and will be removed with subsequent patch.
+			 */
+			spin_unlock(&hugetlb_lock);
 			update_and_free_page(h, page);
+			spin_lock(&hugetlb_lock);
 			ret = 1;
 			break;
 		}
@@ -1810,8 +1818,9 @@  retry:
 		}
 		remove_hugetlb_page(h, page, false);
 		h->max_huge_pages--;
+		spin_unlock(&hugetlb_lock);
 		update_and_free_page(h, head);
-		rc = 0;
+		return 0;
 	}
 out:
 	spin_unlock(&hugetlb_lock);
@@ -2563,22 +2572,34 @@  static void try_to_free_low(struct hstat
 						nodemask_t *nodes_allowed)
 {
 	int i;
+	struct page *page, *next;
+	LIST_HEAD(page_list);
 
 	if (hstate_is_gigantic(h))
 		return;
 
+	/*
+	 * Collect pages to be freed on a list, and free after dropping lock
+	 */
 	for_each_node_mask(i, *nodes_allowed) {
-		struct page *page, *next;
 		struct list_head *freel = &h->hugepage_freelists[i];
 		list_for_each_entry_safe(page, next, freel, lru) {
 			if (count >= h->nr_huge_pages)
-				return;
+				goto out;
 			if (PageHighMem(page))
 				continue;
 			remove_hugetlb_page(h, page, false);
-			update_and_free_page(h, page);
+			list_add(&page->lru, &page_list);
 		}
 	}
+
+out:
+	spin_unlock(&hugetlb_lock);
+	list_for_each_entry_safe(page, next, &page_list, lru) {
+		update_and_free_page(h, page);
+		cond_resched();
+	}
+	spin_lock(&hugetlb_lock);
 }
 #else
 static inline void try_to_free_low(struct hstate *h, unsigned long count,