Re: [RFC PATCH 3/6] mm: page_owner: add support for splitting to any order in split page_owner.

From: Ralph Campbell
Date: Thu Nov 12 2020 - 12:57:28 EST



On 11/11/20 12:40 PM, Zi Yan wrote:
From: Zi Yan <ziy@xxxxxxxxxx>

It adds a new_order parameter to set new page order in page owner.
It prepares for upcoming changes to support split huge page to any lower
order.

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>

Except for a minor fix below, you can add:
Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>

---
include/linux/page_owner.h | 7 ++++---
mm/huge_memory.c | 2 +-
mm/page_alloc.c | 2 +-
mm/page_owner.c | 6 +++---
4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index 3468794f83d2..215cbb159568 100644
--- a/include/linux/page_owner.h
+++ b/include/linux/page_owner.h
@@ -31,10 +31,11 @@ static inline void set_page_owner(struct page *page,
__set_page_owner(page, order, gfp_mask);
}
-static inline void split_page_owner(struct page *page, unsigned int nr)
+static inline void split_page_owner(struct page *page, unsigned int nr,
+ unsigned int new_order)
{
if (static_branch_unlikely(&page_owner_inited))
- __split_page_owner(page, nr);
+ __split_page_owner(page, nr, new_order);
}
static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
{
@@ -60,7 +61,7 @@ static inline void set_page_owner(struct page *page,
{
}
static inline void split_page_owner(struct page *page,
- unsigned int order)
+ unsigned int nr, unsigned int new_order)
{
}
static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f599f5b9bf7f..8b7d771ee962 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2459,7 +2459,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
ClearPageCompound(head);
- split_page_owner(head, nr);
+ split_page_owner(head, nr, 1);

Shouldn't this be 0, not 1?
(new_order not new_nr).

/* See comment in __split_huge_page_tail() */
if (PageAnon(head)) {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d77220615fd5..a9eead0e091a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3284,7 +3284,7 @@ void split_page(struct page *page, unsigned int order)
for (i = 1; i < (1 << order); i++)
set_page_refcounted(page + i);
- split_page_owner(page, 1 << order);
+ split_page_owner(page, 1 << order, 1);

Ditto, 0.

}
EXPORT_SYMBOL_GPL(split_page);

diff --git a/mm/page_owner.c b/mm/page_owner.c
index b735a8eafcdb..2b7f7e9056dc 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -204,7 +204,7 @@ void __set_page_owner_migrate_reason(struct page *page, int reason)
page_owner->last_migrate_reason = reason;
}
-void __split_page_owner(struct page *page, unsigned int nr)
+void __split_page_owner(struct page *page, unsigned int nr, unsigned int new_order)
{
int i;
struct page_ext *page_ext = lookup_page_ext(page);
@@ -213,9 +213,9 @@ void __split_page_owner(struct page *page, unsigned int nr)
if (unlikely(!page_ext))
return;
- for (i = 0; i < nr; i++) {
+ for (i = 0; i < nr; i += (1 << new_order)) {
page_owner = get_page_owner(page_ext);
- page_owner->order = 0;
+ page_owner->order = new_order;
page_ext = page_ext_next(page_ext);
}
}