The patch titled
Subject: mm: remove redundant compound_head() calling
has been added to the -mm tree. Its filename is
mm-remove-redundant-compound_head-calling.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-remove-redundant-compound_head-calling.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-remove-redundant-compound_head-calling.patch
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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm: remove redundant compound_head() calling
There is a READ_ONCE() in the macro of compound_head(), which will prevent
compiler from optimizing the code when there are more than once calling of
it in a function. Remove the redundant calling of compound_head() from
page_to_index() and page_add_file_rmap() for better code generation.
Link: https://lkml.kernel.org/r/20210811101431.83940-1-songmuchun@xxxxxxxxxxxxx
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pagemap.h | 7 +++----
mm/rmap.c | 6 ++++--
2 files changed, 7 insertions(+), 6 deletions(-)
--- a/include/linux/pagemap.h~mm-remove-redundant-compound_head-calling
+++ a/include/linux/pagemap.h
@@ -571,18 +571,17 @@ static inline struct page *read_mapping_
*/
static inline pgoff_t page_to_index(struct page *page)
{
- pgoff_t pgoff;
+ struct page *head;
if (likely(!PageTransTail(page)))
return page->index;
+ head = compound_head(page);
/*
* We don't initialize ->index for tail pages: calculate based on
* head page
*/
- pgoff = compound_head(page)->index;
- pgoff += page - compound_head(page);
- return pgoff;
+ return head->index + page - head;
}
extern pgoff_t hugetlb_basepage_index(struct page *page);
--- a/mm/rmap.c~mm-remove-redundant-compound_head-calling
+++ a/mm/rmap.c
@@ -1230,11 +1230,13 @@ void page_add_file_rmap(struct page *pag
nr_pages);
} else {
if (PageTransCompound(page) && page_mapping(page)) {
+ struct page *head = compound_head(page);
+
VM_WARN_ON_ONCE(!PageLocked(page));
- SetPageDoubleMap(compound_head(page));
+ SetPageDoubleMap(head);
if (PageMlocked(page))
- clear_page_mlock(compound_head(page));
+ clear_page_mlock(head);
}
if (!atomic_inc_and_test(&page->_mapcount))
goto out;
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-remove-redundant-compound_head-calling.patch
