Re: [PATCH v2] mm: madvise: use per_vma lock for MADV_FREE

[SeongJae Park <sj@kernel.org>]

On Wed, 11 Jun 2025 22:47:45 +1200 Barry Song <21cnbao@gmail.com> wrote:

> From: Barry Song <v-songbaohua@oppo.com>
> 
> MADV_FREE is another option, besides MADV_DONTNEED, for dynamic memory
> freeing in user-space native or Java heap memory management. For example,
> jemalloc can be configured to use MADV_FREE, and recent versions of the
> Android Java heap have also increasingly adopted MADV_FREE. Supporting
> per-VMA locking for MADV_FREE thus appears increasingly necessary.
> 
> We have replaced walk_page_range() with walk_page_range_vma(). Along with
> the proposed madvise_lock_mode by Lorenzo, the necessary infrastructure is
> now in place to begin exploring per-VMA locking support for MADV_FREE and
> potentially other madvise using walk_page_range_vma().
> 
> This patch adds support for the PGWALK_VMA_RDLOCK walk_lock mode in
> walk_page_range_vma(), and leverages madvise_lock_mode from
> madv_behavior to select the appropriate walk_lock—either mmap_lock or
> per-VMA lock—based on the context.
> 
> Because we now dynamically update the walk_ops->walk_lock field, we
> must ensure this is thread-safe. The madvise_free_walk_ops is now
> defined as a stack variable instead of a global constant.
> 
> Acked-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Jann Horn <jannh@google.com>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Lokesh Gidra <lokeshgidra@google.com>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Tangquan Zheng <zhengtangquan@oppo.com>
> Cc: Qi Zheng <zhengqi.arch@bytedance.com>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>

Acked-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

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