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Date: Wed, 14 Feb 2024 10:29:40 -0500
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: "\"Pankaj Raghav (Samsung)\"" <kernel@...kajraghav.com>,
linux-mm@...ck.org, "\"Matthew Wilcox (Oracle)\"" <willy@...radead.org>,
Yang Shi <shy828301@...il.com>, Yu Zhao <yuzhao@...gle.com>,
"\"Kirill A . Shutemov\"" <kirill.shutemov@...ux.intel.com>,
Ryan Roberts <ryan.roberts@....com>,
"Michal Koutný" <mkoutny@...e.com>,
Roman Gushchin <roman.gushchin@...ux.dev>,
"\"Zach O'Keefe\"" <zokeefe@...gle.com>, Hugh Dickins <hughd@...gle.com>,
Mcgrof Chamberlain <mcgrof@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: 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@...dia.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@...dia.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
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