Re: [PATCH v4 14/15] mm, swap: implement dynamic allocation of swap table

[Barry Song]

On Wed, Sep 17, 2025 at 12:02 AM Kairui Song <ryncsn@xxxxxxxxx> wrote:
>
> From: Kairui Song <kasong@xxxxxxxxxxx>
>
> Now swap table is cluster based, which means free clusters can free its
> table since no one should modify it.
>
> There could be speculative readers, like swap cache look up, protect
> them by making them RCU protected. All swap table should be filled with
> null entries before free, so such readers will either see a NULL pointer
> or a null filled table being lazy freed.
>
> On allocation, allocate the table when a cluster is used by any order.
>
> This way, we can reduce the memory usage of large swap device
> significantly.
>
> This idea to dynamically release unused swap cluster data was initially
> suggested by Chris Li while proposing the cluster swap allocator and
> it suits the swap table idea very well.
>
> Co-developed-by: Chris Li <chrisl@xxxxxxxxxx>
> Signed-off-by: Chris Li <chrisl@xxxxxxxxxx>
> Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>

Reviewed-by: Barry Song <baohua@xxxxxxxxxx>

Thanks
Barry