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mm-util-reduce-stack-usage-of-folio_mapcount.patch removed from -mm tree

merged mm-stable Andrew Morton 1 participant 1 message Sep 12, 2022

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Andrew Morton

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The quilt patch titled
Subject: mm/util: reduce stack usage of folio_mapcount
has been removed from the -mm tree. Its filename was
mm-util-reduce-stack-usage-of-folio_mapcount.patch

This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Kairui Song <[email protected]>
Subject: mm/util: reduce stack usage of folio_mapcount
Date: Tue, 2 Aug 2022 01:31:55 +0800

folio_test_hugetlb() will call PageHeadHuge which is a function call, and blocks the compiler from recognizing this redundant load.

After rearranging the code, stack usage is dropped from 32 to 24, and the function size is smaller (tested on GCC 12):

Before:
Stack usage:
mm/util.c:845:5:folio_mapcount 32 static
Size:
0000000000000ea0 00000000000000c7 T folio_mapcount

After:
Stack usage:
mm/util.c:845:5:folio_mapcount 24 static
Size:
0000000000000ea0 00000000000000b0 T folio_mapcount

---

 mm/util.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
mm/util.c renamed from mm/util.c~mm-util-reduce-stack-usage-of-folio_mapcount +1 -1
@@ -850,10 +850,10 @@ int folio_mapcount(struct folio *folio)
 		return atomic_read(&folio->_mapcount) + 1;
 
 	compound = folio_entire_mapcount(folio);
-	nr = folio_nr_pages(folio);
 	if (folio_test_hugetlb(folio))
 		return compound;
 	ret = compound;
+	nr = folio_nr_pages(folio);
 	for (i = 0; i < nr; i++)
 		ret += atomic_read(&folio_page(folio, i)->_mapcount) + 1;
 	/* File pages has compound_mapcount included in _mapcount */

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Patches currently in -mm which might be from [email protected] are