linux-kernel - Re: [PATCH v1 3/5] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype

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Date:   Wed, 30 Sep 2020 15:48:16 +0800
From:   Wei Yang <richard.weiyang@...ux.alibaba.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Wei Yang <richard.weiyang@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-hyperv@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-acpi@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...nel.org>,
        Scott Cheloha <cheloha@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v1 3/5] mm/page_alloc: always move pages to the tail of
 the freelist in unset_migratetype_isolate()

On Tue, Sep 29, 2020 at 12:12:14PM +0200, David Hildenbrand wrote:
>On 29.09.20 11:18, Wei Yang wrote:
>> On Mon, Sep 28, 2020 at 08:21:08PM +0200, David Hildenbrand wrote:
>>> Page isolation doesn't actually touch the pages, it simply isolates
>>> pageblocks and moves all free pages to the MIGRATE_ISOLATE freelist.
>>>
>>> We already place pages to the tail of the freelists when undoing
>>> isolation via __putback_isolated_page(), let's do it in any case
>>> (e.g., if order <= pageblock_order) and document the behavior.
>>>
>>> Add a "to_tail" parameter to move_freepages_block() but introduce a
>>> a new move_to_free_list_tail() - similar to add_to_free_list_tail().
>
>s/a a/a/
>
>>>
>>> This change results in all pages getting onlined via online_pages() to
>>> be placed to the tail of the freelist.
>>>
>>> Reviewed-by: Oscar Salvador <osalvador@...e.de>
>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>> Cc: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
>>> Cc: Mel Gorman <mgorman@...hsingularity.net>
>>> Cc: Michal Hocko <mhocko@...nel.org>
>>> Cc: Dave Hansen <dave.hansen@...el.com>
>>> Cc: Vlastimil Babka <vbabka@...e.cz>
>>> Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
>>> Cc: Oscar Salvador <osalvador@...e.de>
>>> Cc: Mike Rapoport <rppt@...nel.org>
>>> Cc: Scott Cheloha <cheloha@...ux.ibm.com>
>>> Cc: Michael Ellerman <mpe@...erman.id.au>
>>> Signed-off-by: David Hildenbrand <david@...hat.com>
>>> ---
>>> include/linux/page-isolation.h |  4 ++--
>>> mm/page_alloc.c                | 35 +++++++++++++++++++++++-----------
>>> mm/page_isolation.c            | 12 +++++++++---
>>> 3 files changed, 35 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
>>> index 572458016331..3eca9b3c5305 100644
>>> --- a/include/linux/page-isolation.h
>>> +++ b/include/linux/page-isolation.h
>>> @@ -36,8 +36,8 @@ static inline bool is_migrate_isolate(int migratetype)
>>> struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>>> 				 int migratetype, int flags);
>>> void set_pageblock_migratetype(struct page *page, int migratetype);
>>> -int move_freepages_block(struct zone *zone, struct page *page,
>>> -				int migratetype, int *num_movable);
>>> +int move_freepages_block(struct zone *zone, struct page *page, int migratetype,
>>> +			 bool to_tail, int *num_movable);
>>>
>>> /*
>>>  * Changes migrate type in [start_pfn, end_pfn) to be MIGRATE_ISOLATE.
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index 9e3ed4a6f69a..d5a5f528b8ca 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -905,6 +905,15 @@ static inline void move_to_free_list(struct page *page, struct zone *zone,
>>> 	list_move(&page->lru, &area->free_list[migratetype]);
>>> }
>>>
>>> +/* Used for pages which are on another list */
>>> +static inline void move_to_free_list_tail(struct page *page, struct zone *zone,
>>> +					  unsigned int order, int migratetype)
>>> +{
>>> +	struct free_area *area = &zone->free_area[order];
>>> +
>>> +	list_move_tail(&page->lru, &area->free_list[migratetype]);
>>> +}
>>> +
>> 
>> Would it be better to pass the *to_tail* to move_to_free_list(), so we won't
>> have a new function?
>
>Hi,
>
>thanks for the review!
>
>See discussion in RFC + cover letter:
>
>"Add a "to_tail" parameter to move_freepages_block() but introduce a new
>move_to_free_list_tail() - similar to add_to_free_list_tail()."

Hmm, sounds reasonable.

Reviewed-by: Wei Yang <richard.weiyang@...ux.alibaba.com>

-- 
Wei Yang
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