Commit 3972f6bb authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
Browse files

mm, debug_pagealloc: use a page type instead of page_ext flag 

When debug_pagealloc is enabled, we currently allocate the page_ext
array to mark guard pages with the PAGE_EXT_DEBUG_GUARD flag.  Now that
we have the page_type field in struct page, we can use that instead, as
guard pages are neither PageSlab nor mapped to userspace.  This reduces
memory overhead when debug_pagealloc is enabled and there are no other
features requiring the page_ext array.

Link: http://lkml.kernel.org/r/20190603143451.27353-4-vbabka@suse.cz


Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4462b32c

Documentation/admin-guide/kernel-parameters.txt

+4 −6
Original line number Diff line number Diff line
@@ -805,12 +805,10 @@ 
			tracking down these problems.



	debug_pagealloc=

			[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this

			parameter enables the feature at boot time. In

			default, it is disabled. We can avoid allocating huge

			chunk of memory for debug pagealloc if we don't enable

			it at boot time and the system will work mostly same

			with the kernel built without CONFIG_DEBUG_PAGEALLOC.

			[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter

			enables the feature at boot time. By default, it is

			disabled and the system will work mostly the same as a

			kernel built without CONFIG_DEBUG_PAGEALLOC.

			on: enable the feature



	debugpat	[X86] Enable PAT debugging

include/linux/mm.h

+1 −9
Original line number Diff line number Diff line
@@ -2862,8 +2862,6 @@ extern long copy_huge_page_from_user(struct page *dst_page, 
				bool allow_pagefault);

#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */



extern struct page_ext_operations debug_guardpage_ops;



#ifdef CONFIG_DEBUG_PAGEALLOC

extern unsigned int _debug_guardpage_minorder;

DECLARE_STATIC_KEY_FALSE(_debug_guardpage_enabled);
@@ -2880,16 +2878,10 @@ static inline bool debug_guardpage_enabled(void) 


static inline bool page_is_guard(struct page *page)

{

	struct page_ext *page_ext;



	if (!debug_guardpage_enabled())

		return false;



	page_ext = lookup_page_ext(page);

	if (unlikely(!page_ext))

		return false;



	return test_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);

	return PageGuard(page);

}

#else

static inline unsigned int debug_guardpage_minorder(void) { return 0; }

include/linux/page-flags.h

+6 −0
Original line number Diff line number Diff line
@@ -703,6 +703,7 @@ PAGEFLAG_FALSE(DoubleMap) 
#define PG_offline	0x00000100

#define PG_kmemcg	0x00000200

#define PG_table	0x00000400

#define PG_guard	0x00000800



#define PageType(page, flag)						\

	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
@@ -754,6 +755,11 @@ PAGE_TYPE_OPS(Kmemcg, kmemcg) 
 */

PAGE_TYPE_OPS(Table, table)



/*

 * Marks guardpages used with debug_pagealloc.

 */

PAGE_TYPE_OPS(Guard, guard)



extern bool is_free_buddy_page(struct page *page);



__PAGEFLAG(Isolated, isolated, PF_ANY);

include/linux/page_ext.h

+0 −1
Original line number Diff line number Diff line
@@ -17,7 +17,6 @@ struct page_ext_operations { 
#ifdef CONFIG_PAGE_EXTENSION



enum page_ext_flags {

	PAGE_EXT_DEBUG_GUARD,

	PAGE_EXT_OWNER,

#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)

	PAGE_EXT_YOUNG,

mm/Kconfig.debug

+0 −1
Original line number Diff line number Diff line
@@ -12,7 +12,6 @@ config DEBUG_PAGEALLOC 
	bool "Debug page memory allocations"

	depends on DEBUG_KERNEL

	depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC

	select PAGE_EXTENSION

	select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC

	---help---

	  Unmap pages from the kernel linear mapping after free_pages().

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