From: "Zi Yan" <ziy@nvidia.com>
To: "Roman Gushchin" <guro@fb.com>, "Matthew Wilcox" <willy@infradead.org>
Cc: linux-mm@kvack.org,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
"Yang Shi" <shy828301@gmail.com>,
"Michal Hocko" <mhocko@kernel.org>,
"John Hubbard" <jhubbard@nvidia.com>,
"Ralph Campbell" <rcampbell@nvidia.com>,
"David Nellans" <dnellans@nvidia.com>
Subject: Re: [RFC PATCH 3/6] mm: page_owner: add support for splitting to any order in split page_owner.
Date: Fri, 13 Nov 2020 20:08:58 -0500 [thread overview]
Message-ID: <F55878E8-22B1-443E-9CC8-E97B3DAA7EA4@nvidia.com> (raw)
In-Reply-To: <20201114001505.GA3047204@carbon.dhcp.thefacebook.com>
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@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 | 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@infradead.org/
—
Best Regards,
Yan Zi
next prev parent reply other threads:[~2020-11-14 1:09 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-11 20:40 [RFC PATCH 0/6] Split huge pages to any lower order pages Zi Yan
2020-11-11 20:40 ` [RFC PATCH 1/6] mm: huge_memory: add new debugfs interface to trigger split huge page on any page range Zi Yan
2020-11-12 22:22 ` Ralph Campbell
2020-11-12 22:38 ` Zi Yan
2020-11-16 16:06 ` Kirill A. Shutemov
2020-11-16 17:26 ` Zi Yan
2020-11-11 20:40 ` [RFC PATCH 2/6] mm: memcg: make memcg huge page split support any order split Zi Yan
2020-11-12 17:58 ` Ralph Campbell
2020-11-12 18:00 ` Zi Yan
2020-11-14 0:23 ` Roman Gushchin
2020-11-14 0:56 ` Zi Yan
2020-11-11 20:40 ` [RFC PATCH 3/6] mm: page_owner: add support for splitting to any order in split page_owner Zi Yan
2020-11-12 17:57 ` Ralph Campbell
2020-11-12 17:59 ` Zi Yan
2020-11-14 0:15 ` Roman Gushchin
2020-11-14 1:08 ` Zi Yan [this message]
2020-11-14 1:38 ` Roman Gushchin
2020-11-17 21:05 ` Matthew Wilcox
2020-11-17 21:12 ` Zi Yan
2020-11-17 21:22 ` Matthew Wilcox
2020-11-17 21:25 ` Zi Yan
2020-11-17 21:35 ` Roman Gushchin
2020-11-17 21:43 ` Matthew Wilcox
2020-11-16 16:25 ` Kirill A. Shutemov
2020-11-16 17:27 ` Zi Yan
2020-11-17 21:10 ` Matthew Wilcox
2020-11-17 21:13 ` Zi Yan
2020-11-11 20:40 ` [RFC PATCH 4/6] mm: thp: add support for split huge page to any lower order pages Zi Yan
2020-11-12 22:01 ` Ralph Campbell
2020-11-12 22:20 ` Zi Yan
2020-11-14 0:52 ` Roman Gushchin
2020-11-14 1:00 ` Zi Yan
2020-11-11 20:40 ` [RFC PATCH 5/6] mm: truncate: split thp to a non-zero order if possible Zi Yan
2020-11-12 22:08 ` Ralph Campbell
2020-11-12 22:37 ` Zi Yan
2020-11-11 20:40 ` [RFC PATCH 6/6] mm: huge_memory: enable debugfs to split huge pages to any order Zi Yan
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