From: Oscar Salvador <osalvador@suse.de>
To: Muchun Song <songmuchun@bytedance.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Muchun Song <muchun.song@linux.dev>,
Michael Ellerman <mpe@ellerman.id.au>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Mike Rapoport <rppt@kernel.org>, Lorenzo Stoakes <ljs@kernel.org>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <chleroy@kernel.org>,
aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com,
linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/4] mm/sparse-vmemmap: Fix DAX vmemmap accounting with optimization
Date: Tue, 21 Apr 2026 06:00:19 +0200 [thread overview]
Message-ID: <aeb2U5tUQQe1YzJY@localhost.localdomain> (raw)
In-Reply-To: <20260421022044.1217503-4-songmuchun@bytedance.com>
On Tue, Apr 21, 2026 at 10:20:43AM +0800, Muchun Song wrote:
> When vmemmap optimization is enabled for DAX, the nr_memmap_pages
> counter in /proc/vmstat is incorrect. The current code always accounts
> for the full, non-optimized vmemmap size, but vmemmap optimization
> reduces the actual number of vmemmap pages by reusing tail pages. This
> causes the system to overcount vmemmap usage, leading to inaccurate
> page statistics in /proc/vmstat.
>
> Fix this by introducing section_vmemmap_pages(), which returns the exact
> vmemmap page count for a given pfn range based on whether optimization
> is in effect.
>
> Fixes: 15995a352474 ("mm: report per-page metadata information")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Oscar Salvador <osalvador@suse.de>
--
Oscar Salvador
SUSE Labs
next prev parent reply other threads:[~2026-04-21 4:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-21 2:20 [PATCH v3 0/4] mm: Fix vmemmap optimization accounting and initialization Muchun Song
2026-04-21 2:20 ` [PATCH v3 1/4] mm/sparse-vmemmap: Fix vmemmap accounting underflow Muchun Song
2026-04-21 3:45 ` Oscar Salvador
2026-04-21 2:20 ` [PATCH v3 2/4] mm/sparse-vmemmap: Pass @pgmap argument to memory deactivation paths Muchun Song
2026-04-21 3:55 ` Oscar Salvador
2026-04-21 4:01 ` Muchun Song
2026-04-21 2:20 ` [PATCH v3 3/4] mm/sparse-vmemmap: Fix DAX vmemmap accounting with optimization Muchun Song
2026-04-21 4:00 ` Oscar Salvador [this message]
2026-04-21 2:20 ` [PATCH v3 4/4] mm/mm_init: Fix pageblock migratetype for ZONE_DEVICE compound pages Muchun Song
2026-04-21 4:15 ` Oscar Salvador
2026-04-21 6:54 ` Muchun Song
2026-04-21 7:29 ` Oscar Salvador
2026-04-21 9:31 ` Muchun Song
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