Re: [PATCH v2 11/11] Documentation/mm: update DAX vmemmap deduplication docs

From: Qi Zheng

Date: Tue Sep 08 2026 - 06:04:27 EST




On 9/8/26 11:03 AM, Muchun Song wrote:
Device DAX now uses the common per-zone shared tail page for vmemmap
deduplication. The old documentation still described a DAX-specific
layout with a separately populated tail vmemmap page and half the HugeTLB
savings.

Update the generic and powerpc documentation to describe the shared layout.
In the powerpc document, keep the radix and 64K-specific details, drop the
duplicated 4K PUD arithmetic, and replace the repeated device-dax diagrams
with a single parameterized PMD/PUD diagram.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
v2:
- Clarify the commit message to state that the 4K PUD arithmetic is
intentionally dropped reported by Sashiko.
---
Documentation/arch/powerpc/vmemmap_dedup.rst | 90 ++++----------------
Documentation/mm/vmemmap_dedup.rst | 32 +------
2 files changed, 21 insertions(+), 101 deletions(-)

Acked-by: Qi Zheng <qi.zheng@xxxxxxxxx>

Thanks,
Qi