The patch titled
Subject: mm: pack compound_dtor and compound_order into one word in struct page
has been added to the -mm tree. Its filename is
mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: pack compound_dtor and compound_order into one word in struct page
The patch halves space occupied by compound_dtor and compound_order in
struct page.
For compound_order, it's trivial long -> short conversion.
For get_compound_page_dtor(), we now use hardcoded table for destructor
lookup and store its index in the struct page instead of direct pointer
to destructor. It shouldn't be a big trouble to maintain the table: we
have only two destructor and NULL currently.
This patch free up one word in tail pages for reuse. This is preparation
for the next patch.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 24 +++++++++++++++++++-----
include/linux/mm_types.h | 6 ++----
mm/hugetlb.c | 8 ++++----
mm/page_alloc.c | 11 ++++++++++-
4 files changed, 35 insertions(+), 14 deletions(-)
diff -puN include/linux/mm.h~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page include/linux/mm.h
--- a/include/linux/mm.h~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page
+++ a/include/linux/mm.h
@@ -568,18 +568,32 @@ int split_free_page(struct page *page);
/*
* Compound pages have a destructor function. Provide a
* prototype for that function and accessor functions.
- * These are _only_ valid on the head of a PG_compound page.
+ * These are _only_ valid on the head of a compound page.
*/
+typedef void compound_page_dtor(struct page *);
+
+/* Keep the enum in sync with compound_page_dtors array in mm/page_alloc.c */
+enum compound_dtor_id {
+ NULL_COMPOUND_DTOR,
+ COMPOUND_PAGE_DTOR,
+#ifdef CONFIG_HUGETLB_PAGE
+ HUGETLB_PAGE_DTOR,
+#endif
+ NR_COMPOUND_DTORS,
+};
+extern compound_page_dtor * const compound_page_dtors[];
static inline void set_compound_page_dtor(struct page *page,
- compound_page_dtor *dtor)
+ enum compound_dtor_id compound_dtor)
{
- page[1].compound_dtor = dtor;
+ VM_BUG_ON_PAGE(compound_dtor >= NR_COMPOUND_DTORS, page);
+ page[1].compound_dtor = compound_dtor;
}
static inline compound_page_dtor *get_compound_page_dtor(struct page *page)
{
- return page[1].compound_dtor;
+ VM_BUG_ON_PAGE(page[1].compound_dtor >= NR_COMPOUND_DTORS, page);
+ return compound_page_dtors[page[1].compound_dtor];
}
static inline int compound_order(struct page *page)
@@ -589,7 +603,7 @@ static inline int compound_order(struct
return page[1].compound_order;
}
-static inline void set_compound_order(struct page *page, unsigned long order)
+static inline void set_compound_order(struct page *page, unsigned int order)
{
page[1].compound_order = order;
}
diff -puN include/linux/mm_types.h~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page include/linux/mm_types.h
--- a/include/linux/mm_types.h~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page
+++ a/include/linux/mm_types.h
@@ -28,8 +28,6 @@ struct mem_cgroup;
IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
-typedef void compound_page_dtor(struct page *);
-
/*
* Each physical page in the system has a struct page associated with
* it to keep track of whatever it is we are using the page for at the
@@ -136,8 +134,8 @@ struct page {
*/
/* First tail page of compound page */
struct {
- compound_page_dtor *compound_dtor;
- unsigned long compound_order;
+ unsigned short int compound_dtor;
+ unsigned short int compound_order;
};
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS
diff -puN mm/hugetlb.c~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page mm/hugetlb.c
--- a/mm/hugetlb.c~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page
+++ a/mm/hugetlb.c
@@ -1146,7 +1146,7 @@ static void update_and_free_page(struct
1 << PG_writeback);
}
VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
- set_compound_page_dtor(page, NULL);
+ set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
set_page_refcounted(page);
if (hstate_is_gigantic(h)) {
destroy_compound_gigantic_page(page, huge_page_order(h));
@@ -1242,7 +1242,7 @@ void free_huge_page(struct page *page)
static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
{
INIT_LIST_HEAD(&page->lru);
- set_compound_page_dtor(page, free_huge_page);
+ set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
spin_lock(&hugetlb_lock);
set_hugetlb_cgroup(page, NULL);
h->nr_huge_pages++;
@@ -1294,7 +1294,7 @@ int PageHuge(struct page *page)
return 0;
page = compound_head(page);
- return get_compound_page_dtor(page) == free_huge_page;
+ return page[1].compound_dtor == HUGETLB_PAGE_DTOR;
}
EXPORT_SYMBOL_GPL(PageHuge);
@@ -1491,7 +1491,7 @@ static struct page *alloc_buddy_huge_pag
if (page) {
INIT_LIST_HEAD(&page->lru);
r_nid = page_to_nid(page);
- set_compound_page_dtor(page, free_huge_page);
+ set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
set_hugetlb_cgroup(page, NULL);
/*
* We incremented the global counters already
diff -puN mm/page_alloc.c~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page mm/page_alloc.c
--- a/mm/page_alloc.c~mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page
+++ a/mm/page_alloc.c
@@ -229,6 +229,15 @@ static char * const zone_names[MAX_NR_ZO
#endif
};
+static void free_compound_page(struct page *page);
+compound_page_dtor * const compound_page_dtors[] = {
+ NULL,
+ free_compound_page,
+#ifdef CONFIG_HUGETLB_PAGE
+ free_huge_page,
+#endif
+};
+
int min_free_kbytes = 1024;
int user_min_free_kbytes = -1;
@@ -458,7 +467,7 @@ void prep_compound_page(struct page *pag
int i;
int nr_pages = 1 << order;
- set_compound_page_dtor(page, free_compound_page);
+ set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
set_compound_order(page, order);
__SetPageHead(page);
for (i = 1; i < nr_pages; i++) {
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
mm-drop-page-slab_page.patch
slab-slub-use-page-rcu_head-instead-of-page-lru-plus-cast.patch
zsmalloc-use-page-private-instead-of-page-first_page.patch
mm-pack-compound_dtor-and-compound_order-into-one-word-in-struct-page.patch
mm-make-compound_head-robust.patch
mm-use-unsigned-int-for-page-order.patch
mm-use-unsigned-int-for-compound_dtor-compound_order-on-64bit.patch
page-flags-trivial-cleanup-for-pagetrans-helpers.patch
page-flags-introduce-page-flags-policies-wrt-compound-pages.patch
page-flags-define-pg_locked-behavior-on-compound-pages.patch
page-flags-define-behavior-of-fs-io-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-lru-related-flags-on-compound-pages.patch
page-flags-define-behavior-slb-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-xen-related-flags-on-compound-pages.patch
page-flags-define-pg_reserved-behavior-on-compound-pages.patch
page-flags-define-pg_swapbacked-behavior-on-compound-pages.patch
page-flags-define-pg_swapcache-behavior-on-compound-pages.patch
page-flags-define-pg_mlocked-behavior-on-compound-pages.patch
page-flags-define-pg_uncached-behavior-on-compound-pages.patch
page-flags-define-pg_uptodate-behavior-on-compound-pages.patch
page-flags-look-on-head-page-if-the-flag-is-encoded-in-page-mapping.patch
mm-sanitize-page-mapping-for-tail-pages.patch
mm-support-madvisemadv_free-fix-3.patch
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