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

Byungchul Park
2025-05-23T07:47:52Z

On Fri, May 23, 2025 at 03:20:27PM +0900, Taehee Yoo wrote:
> 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.

Thanks a lot. I will fix it.

Byungchul
>
> 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
> >
> >