Re: [PATCH v4 4/7] mm: page_owner: add support for splitting to any order in split page_owner.

On 14 Feb 2024, at 4:34, David Hildenbrand wrote:

On 13.02.24 22:55, Zi Yan wrote:

...

From: Zi Yan ziy@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 ziy@nvidia.com

include/linux/page_owner.h | 10 +++++----- mm/huge_memory.c | 2 +- mm/page_alloc.c | 4 ++-- mm/page_owner.c | 9 +++++---- 4 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h index d7878523adfc..a784ba69f67f 100644 --- a/include/linux/page_owner.h +++ b/include/linux/page_owner.h @@ -11,7 +11,7 @@ extern struct page_ext_operations page_owner_ops; extern void __reset_page_owner(struct page *page, unsigned short order); extern void __set_page_owner(struct page *page, unsigned short order, gfp_t gfp_mask); -extern void __split_page_owner(struct page *page, int order); +extern void __split_page_owner(struct page *page, int old_order, int new_order); extern void __folio_copy_owner(struct folio *newfolio, struct folio *old); extern void __set_page_owner_migrate_reason(struct page *page, int reason); extern void __dump_page_owner(const struct page *page); @@ -31,10 +31,10 @@ 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, int order) +static inline void split_page_owner(struct page *page, int old_order, int new_order) { if (static_branch_unlikely(&page_owner_inited))

• __split_page_owner(page, order);
  

• __split_page_owner(page, old_order, new_order);
  

  } static inline void folio_copy_owner(struct folio *newfolio, struct folio *old) {

@@ -56,11 +56,11 @@ static inline void reset_page_owner(struct page *page, unsigned short order) { } static inline void set_page_owner(struct page *page,

• 	unsigned int order, gfp_t gfp_mask)
  

• 	unsigned short order, gfp_t gfp_mask)
  

  { } static inline void split_page_owner(struct page *page,

• 	int order)
  

• 	int old_order, int new_order)
  

  { } static inline void folio_copy_owner(struct folio *newfolio, struct folio *folio)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 3d30eccd3a7f..ad7133c97428 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2919,7 +2919,7 @@ static void __split_huge_page(struct page *page, struct list_head *list, unlock_page_lruvec(lruvec); /* Caller disabled irqs, so they are still disabled here */

• split_page_owner(head, order);

• split_page_owner(head, order, 0); /* See comment in __split_huge_page_tail() */ if (PageAnon(head)) {

diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9d4dd41d0647..e0f107b21c98 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2652,7 +2652,7 @@ 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, order);

• split_page_owner(page, order, 0); split_page_memcg(page, order, 0); } EXPORT_SYMBOL_GPL(split_page);

@@ -4837,7 +4837,7 @@ static void *make_alloc_exact(unsigned long addr, unsigned int order, struct page *page = virt_to_page((void *)addr); struct page *last = page + nr;

• split_page_owner(page, order);
  

• split_page_owner(page, order, 0);
  

  split_page_memcg(page, order, 0); while (page < --last) set_page_refcounted(last);

diff --git a/mm/page_owner.c b/mm/page_owner.c index 1319e402c2cf..ebbffa0501db 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -292,19 +292,20 @@ void __set_page_owner_migrate_reason(struct page *page, int reason) page_ext_put(page_ext); } -void __split_page_owner(struct page *page, int order) +void __split_page_owner(struct page *page, int old_order, int new_order) { int i; struct page_ext *page_ext = page_ext_get(page); struct page_owner *page_owner;

• unsigned int nr = 1 << order;

• unsigned int old_nr = 1 << old_order;
• unsigned int new_nr = 1 << new_order; if (unlikely(!page_ext)) return;

• for (i = 0; i < nr; i++) {

• for (i = 0; i < old_nr; i += new_nr) { page_owner = get_page_owner(page_ext);

• page_owner->order = 0;
  

• page_owner->order = new_order;
  

  page_ext = page_ext_next(page_ext);

Staring at __set_page_owner_handle(), we do set all 1<<order page_exts (corresponding to 1<<order "struct page"s) to have ->order set.

Wouldn't you have to do the same here?

for (i = 0; i < 1 << old_order; i++) { page_owner = get_page_owner(page_ext); page_owner->order = new_order; page_ext = page_ext_next(page_ext); }

You are right. So page owner is per struct page. I misunderstood the code. Thank you for pointing this out. Will fix it.

-- Best Regards, Yan, Zi