[019/166] include/linux/pagemap.h: optimise find_subpage for !THP
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Message ID 20200407030431.Aua57ze5l%akpm@linux-foundation.org
State New
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Series
  • [001/166] mm, memcg: bypass high reclaim iteration for cgroup hierarchy root
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Commit Message

Andrew Morton April 7, 2020, 3:04 a.m. UTC
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: include/linux/pagemap.h: optimise find_subpage for !THP

If THP is disabled, find_subpage() can become a no-op by using
hpage_nr_pages() instead of compound_nr().  hpage_nr_pages() embeds a
check for PageTail, so we can drop the check here.

Link: http://lkml.kernel.org/r/20200318140253.6141-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/pagemap.h |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Patch
diff mbox series

--- a/include/linux/pagemap.h~mm-optimise-find_subpage-for-thp
+++ a/include/linux/pagemap.h
@@ -341,9 +341,7 @@  static inline struct page *find_subpage(
 	if (PageHuge(head))
 		return head;
 
-	VM_BUG_ON_PAGE(PageTail(head), head);
-
-	return head + (index & (compound_nr(head) - 1));
+	return head + (index & (hpage_nr_pages(head) - 1));
 }
 
 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);