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authorJoonsoo Kim <iamjoonsoo.kim@lge.com>2016-10-07 16:58:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-07 18:46:27 -0700
commitacbc15a4b397f86d39416df143e30982b1da528b (patch)
treee5cc9833189325f4ba7c3516b9520f5206fbe9fa
parentbf48438354a79df50fadd2e1c0b81baa2619a8b6 (diff)
mm/debug_pagealloc.c: clean-up guard page handling code
Patch series "Reduce memory waste by page extension user". This patchset tries to reduce memory waste by page extension user. First case is architecture supported debug_pagealloc. It doesn't requires additional memory if guard page isn't used. 8 bytes per page will be saved in this case. Second case is related to page owner feature. Until now, if page_ext users want to use it's own fields on page_ext, fields should be defined in struct page_ext by hard-coding. It has a following problem. struct page_ext { #ifdef CONFIG_A int a; #endif #ifdef CONFIG_B int b; #endif }; Assume that kernel is built with both CONFIG_A and CONFIG_B. Even if we enable feature A and doesn't enable feature B at runtime, each entry of struct page_ext takes two int rather than one int. It's undesirable waste so this patch tries to reduce it. By this patchset, we can save 20 bytes per page dedicated for page owner feature in some configurations. This patch (of 6): We can make code clean by moving decision condition for set_page_guard() into set_page_guard() itself. It will help code readability. There is no functional change. Link: http://lkml.kernel.org/r/1471315879-32294-2-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c34
1 files changed, 18 insertions, 16 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0c34633720c0..e150ba9e1311 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -637,17 +637,20 @@ static int __init debug_guardpage_minorder_setup(char *buf)
}
__setup("debug_guardpage_minorder=", debug_guardpage_minorder_setup);
-static inline void set_page_guard(struct zone *zone, struct page *page,
+static inline bool set_page_guard(struct zone *zone, struct page *page,
unsigned int order, int migratetype)
{
struct page_ext *page_ext;
if (!debug_guardpage_enabled())
- return;
+ return false;
+
+ if (order >= debug_guardpage_minorder())
+ return false;
page_ext = lookup_page_ext(page);
if (unlikely(!page_ext))
- return;
+ return false;
__set_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
@@ -655,6 +658,8 @@ static inline void set_page_guard(struct zone *zone, struct page *page,
set_page_private(page, order);
/* Guard pages are not available for any usage */
__mod_zone_freepage_state(zone, -(1 << order), migratetype);
+
+ return true;
}
static inline void clear_page_guard(struct zone *zone, struct page *page,
@@ -677,8 +682,8 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
}
#else
struct page_ext_operations debug_guardpage_ops = { NULL, };
-static inline void set_page_guard(struct zone *zone, struct page *page,
- unsigned int order, int migratetype) {}
+static inline bool set_page_guard(struct zone *zone, struct page *page,
+ unsigned int order, int migratetype) { return false; }
static inline void clear_page_guard(struct zone *zone, struct page *page,
unsigned int order, int migratetype) {}
#endif
@@ -1622,18 +1627,15 @@ static inline void expand(struct zone *zone, struct page *page,
size >>= 1;
VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
- if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC) &&
- debug_guardpage_enabled() &&
- high < debug_guardpage_minorder()) {
- /*
- * Mark as guard pages (or page), that will allow to
- * merge back to allocator when buddy will be freed.
- * Corresponding page table entries will not be touched,
- * pages will stay not present in virtual address space
- */
- set_page_guard(zone, &page[size], high, migratetype);
+ /*
+ * Mark as guard pages (or page), that will allow to
+ * merge back to allocator when buddy will be freed.
+ * Corresponding page table entries will not be touched,
+ * pages will stay not present in virtual address space
+ */
+ if (set_page_guard(zone, &page[size], high, migratetype))
continue;
- }
+
list_add(&page[size].lru, &area->free_list[migratetype]);
area->nr_free++;
set_page_order(&page[size], high);