[152/155] mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge()

Commit Message

Andrew Morton April 2, 2020, 4:11 a.m. UTC

From: Vlastimil Babka <[e-mail]>
Subject: mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge()

Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one
word in struct page") changed compound_dtor from a pointer to an array
index in order to pack it.  To check if page has the hugeltbfs
compound_dtor, we can just compare the index directly without fetching the
function pointer.  Said commit did that with PageHuge() and we can do the
same with PageHeadHuge() to make the code a bit smaller and faster.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Reviewed-by: Mike Kravetz <[e-mail]>
Acked-by: David Rientjes <[e-mail]>
Acked-by: Kirill A. Shutemov <[e-mail]>
Cc: Neha Agarwal <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/hugetlb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

--- a/mm/hugetlb.c~mm-hugetlb-remove-unnecessary-memory-fetch-in-pageheadhuge
+++ a/mm/hugetlb.c
@@ -1528,7 +1528,7 @@  int PageHeadHuge(struct page *page_head)
 	if (!PageHead(page_head))
 		return 0;
 
-	return get_compound_page_dtor(page_head) == free_huge_page;
+	return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR;
 }
 
 /*