linux-kernel - Re: [PATCH 3/8] mm: Introduce PageUnaccepted() page type

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Message-ID: <56be9c2c-6f44-409f-bb66-3bb488f0d546@redhat.com>
Date: Tue, 6 Aug 2024 14:06:02 +0200
From: David Hildenbrand <david@...hat.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 "Borislav Petkov (AMD)" <bp@...en8.de>, Mel Gorman <mgorman@...e.de>,
 Vlastimil Babka <vbabka@...e.cz>
Cc: Tom Lendacky <thomas.lendacky@....com>, Mike Rapoport <rppt@...nel.org>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] mm: Introduce PageUnaccepted() page type

On 05.08.24 16:59, Kirill A. Shutemov wrote:
> The new page type allows physical memory scanners to detect unaccepted
> memory and handle it accordingly.
> 
> The page type is serialized with zone lock.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>   include/linux/page-flags.h | 3 +++
>   mm/page_alloc.c            | 2 ++
>   2 files changed, 5 insertions(+)
> 
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 5769fe6e4950..e19eac9c2b5c 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -943,6 +943,7 @@ enum pagetype {
>   	PG_hugetlb	= 0x04000000,
>   	PG_slab		= 0x02000000,
>   	PG_zsmalloc	= 0x01000000,
> +	PG_unaccepted	= 0x00800000,
>   
>   	PAGE_TYPE_BASE	= 0x80000000,
>   
> @@ -1076,6 +1077,8 @@ FOLIO_TEST_FLAG_FALSE(hugetlb)
>   
>   PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc)
>   
> +PAGE_TYPE_OPS(Unaccepted, unaccepted, unaccepted)

I'm sure you're able to come up with some documentation ;)

> +
>   /**
>    * PageHuge - Determine if the page belongs to hugetlbfs
>    * @page: The page to test.
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 90a1f01d5996..a35efb114496 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6972,6 +6972,7 @@ static bool try_to_accept_memory_one(struct zone *zone)
>   
>   	account_freepages(zone, -MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
>   	__mod_zone_page_state(zone, NR_UNACCEPTED, -MAX_ORDER_NR_PAGES);
> +	__ClearPageUnaccepted(page);
>   	spin_unlock_irqrestore(&zone->lock, flags);
>   
>   	accept_page(page, MAX_PAGE_ORDER);
> @@ -7030,6 +7031,7 @@ static bool __free_unaccepted(struct page *page)
>   	list_add_tail(&page->lru, &zone->unaccepted_pages);
>   	account_freepages(zone, MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
>   	__mod_zone_page_state(zone, NR_UNACCEPTED, MAX_ORDER_NR_PAGES);
> +	__SetPageUnaccepted(page);
>   	spin_unlock_irqrestore(&zone->lock, flags);
>   
>   	if (first)

At the point PG_unaccepted is set/cleared, we don't have another type 
set, right? (IOW, PG_buddy is only set after we cleared PG_unaccepted)

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb