On 13 Nov 2020, at 19:15, Roman Gushchin wrote:
On Wed, Nov 11, 2020 at 03:40:05PM -0500, 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>
---
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)
With the addition of the new argument it's a bit hard to understand
what the function is supposed to do. It seems like nr ==
page_order(page),
is it right? Maybe we can pass old_order and new_order? Or just the
page
and the new order?
Yeah, it is a bit confusing. Please see more below.
{
}
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);
/* 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);
}
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);
I believe there cannot be any leftovers because nr is always a power
of 2.
Is it true? Converting nr argument to order (if it's possible) will
make it obvious.
Right. nr = thp_nr_pages(head), which is a power of 2. There would not
be any
leftover.
Matthew recently converted split_page_owner to take nr instead of
order.[1] But I am not
sure why, since it seems to me that two call sites (__split_huge_page in
mm/huge_memory.c and split_page in mm/page_alloc.c) can pass the order
information.
[1]https://lore.kernel.org/linux-mm/20200908195539.25896-4-willy@xxxxxxxxxxxxx/
—
Best Regards,
Yan Zi
