Re: [PATCH 00/18] Split netmem from struct page

[Taehee Yoo <ap420073@gmail.com>]

On Fri, May 23, 2025 at 12:36 PM Byungchul Park <byungchul@sk.com> wrote:
>

Hi Byungchul,
Thanks a lot for this work!

> The MM subsystem is trying to reduce struct page to a single pointer.
> The first step towards that is splitting struct page by its individual
> users, as has already been done with folio and slab.  This patchset does
> that for netmem which is used for page pools.
>
> Matthew Wilcox tried and stopped the same work, you can see in:
>
>    https://lore.kernel.org/linux-mm/20230111042214.907030-1-willy@infradead.org/
>
> Mina Almasry already has done a lot fo prerequisite works by luck, he
> said :).  I stacked my patches on the top of his work e.i. netmem.
>
> I focused on removing the page pool members in struct page this time,
> not moving the allocation code of page pool from net to mm.  It can be
> done later if needed.
>
> My rfc version of this work is:
>
>    https://lore.kernel.org/all/20250509115126.63190-1-byungchul@sk.com/
>
> There are still a lot of works to do, to remove the dependency on struct
> page in the network subsystem.  I will continue to work on this after
> this base patchset is merged.

There is a compile failure.

In file included from drivers/net/ethernet/intel/libeth/rx.c:4:
./include/net/libeth/rx.h: In function ‘libeth_rx_sync_for_cpu’:
./include/net/libeth/rx.h:140:40: error: ‘struct page’ has no member named ‘pp’
  140 |         page_pool_dma_sync_for_cpu(page->pp, page, fqe->offset, len);
      |                                        ^~
drivers/net/ethernet/intel/libeth/rx.c: In function ‘libeth_rx_recycle_slow’:
drivers/net/ethernet/intel/libeth/rx.c:210:38: error: ‘struct page’
has no member named ‘pp’
  210 |         page_pool_recycle_direct(page->pp, page);
      |                                      ^~
make[7]: *** [scripts/Makefile.build:203:
drivers/net/ethernet/intel/libeth/rx.o] Error 1
make[6]: *** [scripts/Makefile.build:461:
drivers/net/ethernet/intel/libeth] Error 2
make[5]: *** [scripts/Makefile.build:461: drivers/net/ethernet/intel] Error 2
make[5]: *** Waiting for unfinished jobs....

There are page->pp usecases in drivers/net
./drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c:1574:
 } else if (page->pp) {
./drivers/net/ethernet/freescale/fec_main.c:1046:
                 page_pool_put_page(page->pp, page, 0, false);
./drivers/net/ethernet/freescale/fec_main.c:1584:
 page_pool_put_page(page->pp, page, 0, true);
./drivers/net/ethernet/freescale/fec_main.c:3351:
         page_pool_put_page(page->pp, page, 0, false);
./drivers/net/ethernet/ti/icssg/icssg_prueth_sr1.c:370:
page_pool_recycle_direct(page->pp, page);
./drivers/net/ethernet/ti/icssg/icssg_prueth_sr1.c:395:
page_pool_recycle_direct(page->pp, page);
./drivers/net/ethernet/ti/icssg/icssg_common.c:111:
page_pool_recycle_direct(page->pp, swdata->data.page);
./drivers/net/ethernet/intel/idpf/idpf_txrx.c:389:
page_pool_put_full_page(rx_buf->page->pp, rx_buf->page, false);
./drivers/net/ethernet/intel/idpf/idpf_txrx.c:3254:     u32 hr =
rx_buf->page->pp->p.offset;
./drivers/net/ethernet/intel/idpf/idpf_txrx.c:3286:     dst =
page_address(hdr->page) + hdr->offset + hdr->page->pp->p.offset;
./drivers/net/ethernet/intel/idpf/idpf_txrx.c:3287:     src =
page_address(buf->page) + buf->offset + buf->page->pp->p.offset;
./drivers/net/ethernet/intel/idpf/idpf_txrx.c:3305:     u32 hr =
buf->page->pp->p.offset;
./drivers/net/ethernet/intel/libeth/rx.c:210:
page_pool_recycle_direct(page->pp, page);
./drivers/net/ethernet/intel/iavf/iavf_txrx.c:1200:     u32 hr =
rx_buffer->page->pp->p.offset;
./drivers/net/ethernet/intel/iavf/iavf_txrx.c:1217:     u32 hr =
rx_buffer->page->pp->p.offset;
./drivers/net/wireless/mediatek/mt76/mt76.h:1800:
page_pool_put_full_page(page->pp, page, allow_direct);
./include/net/libeth/rx.h:140:  page_pool_dma_sync_for_cpu(page->pp,
page, fqe->offset, len);

Thanks a lot!
Taehee Yoo

>
> ---
>
> Changes from rfc:
>         1. Rebase on net-next's main branch
>            https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/
>         2. Fix a build error reported by kernel test robot
>            https://lore.kernel.org/all/202505100932.uzAMBW1y-lkp@intel.com/
>         3. Add given 'Reviewed-by's, thanks to Mina and Ilias
>         4. Do static_assert() on the size of struct netmem_desc instead
>            of placing place-holder in struct page, feedbacked by Matthew
>         5. Do struct_group_tagged(netmem_desc) on struct net_iov instead
>            of wholly renaming it to strcut netmem_desc, feedbacked by
>            Mina and Pavel
>
> Byungchul Park (18):
>   netmem: introduce struct netmem_desc struct_group_tagged()'ed on
>     struct net_iov
>   netmem: introduce netmem alloc APIs to wrap page alloc APIs
>   page_pool: use netmem alloc/put APIs in __page_pool_alloc_page_order()
>   page_pool: rename __page_pool_alloc_page_order() to
>     __page_pool_alloc_large_netmem()
>   page_pool: use netmem alloc/put APIs in __page_pool_alloc_pages_slow()
>   page_pool: rename page_pool_return_page() to page_pool_return_netmem()
>   page_pool: use netmem put API in page_pool_return_netmem()
>   page_pool: rename __page_pool_release_page_dma() to
>     __page_pool_release_netmem_dma()
>   page_pool: rename __page_pool_put_page() to __page_pool_put_netmem()
>   page_pool: rename __page_pool_alloc_pages_slow() to
>     __page_pool_alloc_netmems_slow()
>   mlx4: use netmem descriptor and APIs for page pool
>   page_pool: use netmem APIs to access page->pp_magic in
>     page_pool_page_is_pp()
>   mlx5: use netmem descriptor and APIs for page pool
>   netmem: use _Generic to cover const casting for page_to_netmem()
>   netmem: remove __netmem_get_pp()
>   page_pool: make page_pool_get_dma_addr() just wrap
>     page_pool_get_dma_addr_netmem()
>   netdevsim: use netmem descriptor and APIs for page pool
>   mm, netmem: remove the page pool members in struct page
>
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c    |  46 ++++----
>  drivers/net/ethernet/mellanox/mlx4/en_tx.c    |   8 +-
>  drivers/net/ethernet/mellanox/mlx4/mlx4_en.h  |   4 +-
>  drivers/net/ethernet/mellanox/mlx5/core/en.h  |   4 +-
>  .../net/ethernet/mellanox/mlx5/core/en/xdp.c  |  18 ++--
>  .../net/ethernet/mellanox/mlx5/core/en/xdp.h  |   2 +-
>  .../net/ethernet/mellanox/mlx5/core/en_main.c |  15 ++-
>  .../net/ethernet/mellanox/mlx5/core/en_rx.c   |  66 ++++++------
>  drivers/net/netdevsim/netdev.c                |  18 ++--
>  drivers/net/netdevsim/netdevsim.h             |   2 +-
>  include/linux/mm.h                            |   5 +-
>  include/linux/mm_types.h                      |  11 --
>  include/linux/skbuff.h                        |  14 +++
>  include/net/netmem.h                          | 101 ++++++++++--------
>  include/net/page_pool/helpers.h               |  11 +-
>  net/core/page_pool.c                          |  97 +++++++++--------
>  16 files changed, 221 insertions(+), 201 deletions(-)
>
>
> base-commit: f44092606a3f153bb7e6b277006b1f4a5b914cfc
> --
> 2.17.1
>
>