linux-kernel - Re: [PATCH -next v2 1/2] mm: compaction: convert to use a folio in isolate_migratepages

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Message-ID: <58d0d829-da04-0f77-eedf-8bfa519b52f0@linux.alibaba.com>
Date:   Wed, 21 Jun 2023 17:11:15 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        willy@...radead.org, jgowans@...zon.com, yuzhao@...gle.com
Subject: Re: [PATCH -next v2 1/2] mm: compaction: convert to use a folio in
 isolate_migratepages_block()



On 6/21/2023 4:36 PM, Kefeng Wang wrote:
> 
> 
> On 2023/6/21 14:20, Baolin Wang wrote:
>> Hi
>>
>> On 6/19/2023 7:07 PM, Kefeng Wang wrote:
>>> Directly use a folio instead of page_folio() when page successfully
>>> isolated (hugepage and movable page) and after folio_get_nontail_page(),
>>> which removes several calls to compound_head().
>>>
>>> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>>> ---
>>> v2:
>>> - update comments and use node_stat_mod_folio, per Matthew Wilcox
>>> - add missed PageLRU conversion and rebase on next-20230619
>>>
>>>   mm/compaction.c | 84 ++++++++++++++++++++++++++-----------------------
>>>   1 file changed, 44 insertions(+), 40 deletions(-)
>>>
>>> diff --git a/mm/compaction.c b/mm/compaction.c
>>> index 6149a2d324be..0334eefe4bfa 100644
>>> --- a/mm/compaction.c
>>> +++ b/mm/compaction.c
>>> @@ -795,6 +795,7 @@ isolate_migratepages_block(struct compact_control 
>>> *cc, unsigned long low_pfn,
>>>       struct lruvec *lruvec;
>>>       unsigned long flags = 0;
>>>       struct lruvec *locked = NULL;
>>> +    struct folio *folio = NULL;
>>>       struct page *page = NULL, *valid_page = NULL;
>>>       struct address_space *mapping;
>>>       unsigned long start_pfn = low_pfn;
>>> @@ -891,7 +892,7 @@ isolate_migratepages_block(struct compact_control 
>>> *cc, unsigned long low_pfn,
>>>           if (!valid_page && pageblock_aligned(low_pfn)) {
>>>               if (!isolation_suitable(cc, page)) {
>>>                   low_pfn = end_pfn;
>>> -                page = NULL;
>>> +                folio = NULL;
>>>                   goto isolate_abort;
>>>               }
>>>               valid_page = page;
>>> @@ -923,7 +924,8 @@ isolate_migratepages_block(struct compact_control 
>>> *cc, unsigned long low_pfn,
>>>                    * Hugepage was successfully isolated and placed
>>>                    * on the cc->migratepages list.
>>>                    */
>>> -                low_pfn += compound_nr(page) - 1;
>>> +                folio = page_folio(page);
>>> +                low_pfn += folio_nr_pages(folio) - 1;
>>>                   goto isolate_success_no_list;
>>>               }
>>> @@ -991,8 +993,10 @@ isolate_migratepages_block(struct 
>>> compact_control *cc, unsigned long low_pfn,
>>>                       locked = NULL;
>>>                   }
>>> -                if (isolate_movable_page(page, mode))
>>> +                if (isolate_movable_page(page, mode)) {
>>> +                    folio = page_folio(page);
>>>                       goto isolate_success;
>>> +                }
>>>               }
>>>               goto isolate_fail;
>>> @@ -1003,7 +1007,8 @@ isolate_migratepages_block(struct 
>>> compact_control *cc, unsigned long low_pfn,
>>>            * sure the page is not being freed elsewhere -- the
>>>            * page release code relies on it.
>>>            */
>>> -        if (unlikely(!get_page_unless_zero(page)))
>>> +        folio = folio_get_nontail_page(page);
>>
>> I'm just curious, how can you make sure the 'page' is not a tail page? 
>> Since the validation is lockless.
> 
> folio_get_nontail_page is added by commit "3c1ea2c729ef (mm: add
> folio_get_nontail_page())", see more comments [1]
> 
> [1] https://lore.kernel.org/lkml/Y86sRiKAAOz2myNe@casper.infradead.org/

I see. Thanks for sharing. The changes look good to me at least. Please 
feel free to add:
Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>