[PATCH v2] mm/hugetlb: avoid unnecessary hugetlb_acct_memory() call

[Miaohe Lin]

When gbl_reserve is 0, hugetlb_acct_memory() will do nothing except holding
and releasing hugetlb_lock. We should avoid this unnecessary hugetlb_lock
lock/unlock cycle which is happening on 'most' hugetlb munmap operations by
check delta against 0 at the beginning of hugetlb_acct_memory.

Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
 mm/hugetlb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4f67f6b159c7..da064cb8fd53 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3591,6 +3591,9 @@ static int hugetlb_acct_memory(struct hstate *h, long delta)
 {
 	int ret = -ENOMEM;
 
+	if (!delta)
+		return 0;
+
 	spin_lock(&hugetlb_lock);
 	/*
 	 * When cpuset is configured, it breaks the strict hugetlb page
-- 
2.19.1