[PATCH] mm: uninline slowpath of page_mapcount()

[Kirill A. Shutemov]

Let's move page_mapcount() part for compound page into mm/util.c.

make allyesconfig:

  text	   data	    bss	    dec	    hex	filename
188515051	153360535	85458720	427334306	19789aa2	vmlinux.o.before
188512917	153356439	85458720	427328076	1978824c	vmlinux.o.after

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 include/linux/mm.h | 14 +++++---------
 mm/util.c          | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f874d2a1d1a6..72edbbec7b91 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -417,19 +417,15 @@ static inline void page_mapcount_reset(struct page *page)
 	atomic_set(&(page)->_mapcount, -1);
 }
 
+int __page_mapcount(struct page *page);
+
 static inline int page_mapcount(struct page *page)
 {
-	int ret;
 	VM_BUG_ON_PAGE(PageSlab(page), page);
 
-	ret = atomic_read(&page->_mapcount) + 1;
-	if (PageCompound(page)) {
-		page = compound_head(page);
-		ret += atomic_read(compound_mapcount_ptr(page)) + 1;
-		if (PageDoubleMap(page))
-			ret--;
-	}
-	return ret;
+	if (unlikely(PageCompound(page)))
+		return __page_mapcount(page);
+	return atomic_read(&page->_mapcount) + 1;
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
diff --git a/mm/util.c b/mm/util.c
index 902b65a43899..68535c0bb9da 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -376,6 +376,20 @@ struct address_space *page_mapping(struct page *page)
 	return mapping;
 }
 
+/* Slow path of page_mapcount() for compound pages */
+int __page_mapcount(struct page *page)
+{
+	int ret;
+
+	page = compound_head(page);
+	ret = atomic_read(&page->_mapcount) + 1;
+	ret += atomic_read(compound_mapcount_ptr(page)) + 1;
+	if (PageDoubleMap(page))
+		ret--;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__page_mapcount);
+
 int overcommit_ratio_handler(struct ctl_table *table, int write,
 			     void __user *buffer, size_t *lenp,
 			     loff_t *ppos)
-- 
 Kirill A. Shutemov
--
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