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

[Ralph Campbell]

On 11/11/20 12:40 PM, Zi Yan wrote:

From: Zi Yan <z...@nvidia.com>

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 <z...@nvidia.com>

Except for a minor fix below, you can add:
Reviewed-by: Ralph Campbell <rcampb...@nvidia.com>

---
  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);
        }
  }