linux-kernel - Re: [PATCH v4 1/7] mm/memcg: use order instead of nr in split_page

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Message-ID: <1110486E-73BE-44AE-A290-BC8AE1F06F8A@nvidia.com>
Date: Wed, 14 Feb 2024 10:19:21 -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 1/7] mm/memcg: use order instead of nr in
 split_page_memcg()

On 14 Feb 2024, at 4:12, David Hildenbrand wrote:

> On 13.02.24 22:55, Zi Yan wrote:
>> From: Zi Yan <ziy@...dia.com>
>>
>> We do not have non power of two pages, using nr is error prone if nr
>> is not power-of-two. Use page order instead.
>>
>> Signed-off-by: Zi Yan <ziy@...dia.com>
>> ---
>>   include/linux/memcontrol.h | 4 ++--
>>   mm/huge_memory.c           | 3 ++-
>>   mm/memcontrol.c            | 3 ++-
>>   mm/page_alloc.c            | 4 ++--
>>   4 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>> index 4e4caeaea404..173bbb53c1ec 100644
>> --- a/include/linux/memcontrol.h
>> +++ b/include/linux/memcontrol.h
>> @@ -1163,7 +1163,7 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm,
>>   	rcu_read_unlock();
>>   }
>>  -void split_page_memcg(struct page *head, unsigned int nr);
>> +void split_page_memcg(struct page *head, int order);
>>    unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
>>   						gfp_t gfp_mask,
>> @@ -1621,7 +1621,7 @@ void count_memcg_event_mm(struct mm_struct *mm, enum vm_event_item idx)
>>   {
>>   }
>>  -static inline void split_page_memcg(struct page *head, unsigned int nr)
>> +static inline void split_page_memcg(struct page *head, int order)
>>   {
>>   }
>>  diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 016e20bd813e..0cd5fba0923c 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -2877,9 +2877,10 @@ static void __split_huge_page(struct page *page, struct list_head *list,
>>   	unsigned long offset = 0;
>>   	unsigned int nr = thp_nr_pages(head);
>>   	int i, nr_dropped = 0;
>> +	int order = folio_order(folio);
>
> You could calculate "nr" from "order" here, removing the usage of thp_nr_pages().

Sure.

>
>>    	/* complete memcg works before add pages to LRU */
>> -	split_page_memcg(head, nr);
>> +	split_page_memcg(head, order);
>>    	if (folio_test_anon(folio) && folio_test_swapcache(folio)) {
>
> Acked-by: David Hildenbrand <david@...hat.com>

Thanks.

--
Best Regards,
Yan, Zi

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