[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <819b61fb-ebb0-4ded-a104-01ab133b6a41@redhat.com>
Date: Wed, 2 Jul 2025 13:04:05 +0200
From: David Hildenbrand <david@...hat.com>
To: Harry Yoo <harry.yoo@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
virtualization@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>, Jonathan Corbet <corbet@....net>,
Madhavan Srinivasan <maddy@...ux.ibm.com>,
Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Jerrin Shaji George <jerrin.shaji-george@...adcom.com>,
Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
<eperezma@...hat.com>, Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
Zi Yan <ziy@...dia.com>, Matthew Brost <matthew.brost@...el.com>,
Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
Byungchul Park <byungchul@...com>, Gregory Price <gourry@...rry.net>,
Ying Huang <ying.huang@...ux.alibaba.com>,
Alistair Popple <apopple@...dia.com>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
<vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Minchan Kim <minchan@...nel.org>,
Sergey Senozhatsky <senozhatsky@...omium.org>,
Brendan Jackman <jackmanb@...gle.com>, Johannes Weiner <hannes@...xchg.org>,
Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>,
Peter Xu <peterx@...hat.com>, Xu Xin <xu.xin16@....com.cn>,
Chengming Zhou <chengming.zhou@...ux.dev>, Miaohe Lin
<linmiaohe@...wei.com>, Naoya Horiguchi <nao.horiguchi@...il.com>,
Oscar Salvador <osalvador@...e.de>, Rik van Riel <riel@...riel.com>,
Qi Zheng <zhengqi.arch@...edance.com>, Shakeel Butt <shakeel.butt@...ux.dev>
Subject: Re: [PATCH v1 19/29] mm: stop storing migration_ops in page->mapping
On 02.07.25 12:34, Harry Yoo wrote:
> On Mon, Jun 30, 2025 at 03:00:00PM +0200, David Hildenbrand wrote:
>> ... instead, look them up statically based on the page type. Maybe in the
>> future we want a registration interface? At least for now, it can be
>> easily handled using the two page types that actually support page
>> migration.
>>
>> The remaining usage of page->mapping is to flag such pages as actually
>> being movable (having movable_ops), which we will change next.
>>
>> Reviewed-by: Zi Yan <ziy@...dia.com>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
>> ---
>
>> +static const struct movable_operations *page_movable_ops(struct page *page)
>> +{
>> + VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page);
>> +
>> + /*
>> + * If we enable page migration for a page of a certain type by marking
>> + * it as movable, the page type must be sticky until the page gets freed
>> + * back to the buddy.
>> + */
>> +#ifdef CONFIG_BALLOON_COMPACTION
>> + if (PageOffline(page))
>> + /* Only balloon compaction sets PageOffline pages movable. */
>> + return &balloon_mops;
>> +#endif /* CONFIG_BALLOON_COMPACTION */
>> +#if defined(CONFIG_ZSMALLOC) && defined(CONFIG_COMPACTION)
>> + if (PageZsmalloc(page))
>> + return &zsmalloc_mops;
>> +#endif /* defined(CONFIG_ZSMALLOC) && defined(CONFIG_COMPACTION) */
>
> What happens if:
> CONFIG_ZSMALLOC=y
> CONFIG_TRANSPARENT_HUGEPAGE=n
> CONFIG_COMPACTION=n
> CONFIG_MIGRATION=y
Pages are never allocated from ZONE_MOVABLE/CMA and are not marked as
having movable_ops, so we never end up in this function. See how
zsmalloc.c deals with CONFIG_COMPACTION, especially how
SetZsPageMovable() is a NOP without it.
As a side note, both should probably be moved from COMPACTION to
MIGRATION. Although probably in practice, anybody enabling
CONFIG_MIGRATION likely also enables CONFIG_COMPACTION.
--
Cheers,
David / dhildenb
Powered by blists - more mailing lists