From: Qi Zheng <qi.zheng@linux.dev>
To: Muchun Song <songmuchun@bytedance.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Oscar Salvador <osalvador@suse.de>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Jonathan Corbet <corbet@lwn.net>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org,
Muchun Song <muchun.song@linux.dev>,
Lorenzo Stoakes <ljs@kernel.org>, Mike Rapoport <rppt@kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <chleroy@kernel.org>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH 06/11] mm/sparse-vmemmap: switch device DAX to shared tail vmemmap pages
Date: Sat, 5 Sep 2026 16:35:31 +0800 [thread overview]
Message-ID: <e3d0eaf8-a85f-48ff-96c2-dced4945b085@linux.dev> (raw)
In-Reply-To: <20260831075342.57563-7-songmuchun@bytedance.com>
On 8/31/26 3:53 PM, Muchun Song wrote:
> HugeTLB vmemmap optimization now uses per-zone shared tail vmemmap pages.
> Device DAX has not been switched to that mechanism yet.
>
> Switch device DAX to vmemmap_shared_tail_page() as well. This aligns DAX
> with HugeTLB by using the common per-zone shared tail vmemmap page.
>
> Since the shared tail page can now back ZONE_DEVICE vmemmap mappings,
Could you explain this in more detail?
As sashiko pointed out [1], it looks like this assumption is
problematic: dax_folio_reset_order() may end up modifying all shared
tail pages?
[1].
https://sashiko.dev/#/patchset/20260831075342.57563-1-songmuchun%40bytedance.com
> initialize its entries with PG_reserved for device zones. Also skip
> poisoning vmemmap-optimizable sections while their struct pages may be
> shared.
>
next prev parent reply other threads:[~2026-09-05 8:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-31 7:53 [PATCH 00/11] mm: Switch device DAX to section-based vmemmap optimization Muchun Song
2026-08-31 7:53 ` [PATCH 01/11] mm/sparse-vmemmap: introduce CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION Muchun Song
2026-08-31 9:44 ` Qi Zheng
2026-08-31 9:49 ` Muchun Song
2026-08-31 7:53 ` [PATCH 02/11] mm/sparse-vmemmap: factor out shared vmemmap tail page allocation Muchun Song
2026-09-01 3:05 ` Qi Zheng
2026-08-31 7:53 ` [PATCH 03/11] mm/sparse-vmemmap: open-code init_compound_tail() Muchun Song
2026-09-01 3:18 ` Qi Zheng
2026-08-31 7:53 ` [PATCH 04/11] mm/sparse-vmemmap: prepare DAX vmemmap population for section orders Muchun Song
2026-09-03 6:36 ` Qi Zheng
2026-08-31 7:53 ` [PATCH 05/11] mm/sparse-vmemmap: set section order for device DAX Muchun Song
2026-09-05 8:20 ` Qi Zheng
2026-09-05 9:00 ` Muchun Song
2026-08-31 7:53 ` [PATCH 06/11] mm/sparse-vmemmap: switch device DAX to shared tail vmemmap pages Muchun Song
2026-09-05 8:35 ` Qi Zheng [this message]
2026-09-05 9:08 ` Muchun Song
2026-08-31 7:53 ` [PATCH 07/11] mm/sparse-vmemmap: move HVO helpers to a public header Muchun Song
2026-08-31 7:53 ` [PATCH 08/11] powerpc/mm: switch device DAX to shared tail vmemmap pages Muchun Song
2026-08-31 7:53 ` [PATCH 09/11] mm/sparse-vmemmap: drop the extra tail page from device DAX reservation Muchun Song
2026-08-31 7:53 ` [PATCH 10/11] mm/sparse-vmemmap: drop unused section_nr_vmemmap_pages() arguments Muchun Song
2026-08-31 7:53 ` [PATCH 11/11] Documentation/mm: update DAX vmemmap deduplication docs Muchun Song
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