[043/118] mm/rmap: use page_not_mapped in try_to_unmap()

Commit Message

Andrew Morton Feb. 26, 2021, 1:18 a.m. UTC

From: Miaohe Lin <[e-mail]>
Subject: mm/rmap: use page_not_mapped in try_to_unmap()

page_mapcount_is_zero() calculates accurately how many mappings a hugepage
has in order to check against 0 only.  This is a waste of cpu time.  We
can do this via page_not_mapped() to save some possible atomic_read
cycles.  Remove the function page_mapcount_is_zero() as it's not used
anymore and move page_not_mapped() above try_to_unmap() to avoid
identifier undeclared compilation error.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Miaohe Lin <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/rmap.c |   11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

Patch

--- a/mm/rmap.c~mm-rmap-use-page_not_mapped-in-try_to_unmap
+++ a/mm/rmap.c
@@ -1736,9 +1736,9 @@  static bool invalid_migration_vma(struct
 	return vma_is_temporary_stack(vma);
 }
 
-static int page_mapcount_is_zero(struct page *page)
+static int page_not_mapped(struct page *page)
 {
-	return !total_mapcount(page);
+	return !page_mapped(page);
 }
 
 /**
@@ -1756,7 +1756,7 @@  bool try_to_unmap(struct page *page, enu
 	struct rmap_walk_control rwc = {
 		.rmap_one = try_to_unmap_one,
 		.arg = (void *)flags,
-		.done = page_mapcount_is_zero,
+		.done = page_not_mapped,
 		.anon_lock = page_lock_anon_vma_read,
 	};
 
@@ -1780,11 +1780,6 @@  bool try_to_unmap(struct page *page, enu
 	return !page_mapcount(page) ? true : false;
 }
 
-static int page_not_mapped(struct page *page)
-{
-	return !page_mapped(page);
-}
-
 /**
  * try_to_munlock - try to munlock a page
  * @page: the page to be munlocked