mm/hugetlb: avoid unnecessary hugetlb_acct_memory() call

When reservation accounting remains unchanged, 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.

Link: https://lkml.kernel.org/r/20210115092013.61012-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.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 66edef5..0173f9f 100644 (file)
--- 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