From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.hynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9596578F4B; Mon, 9 Jun 2025 06:50:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.125.252.92 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749451806; cv=none; b=W5PW1w3o0400sEVDnW4L8M/RicOfe9UrqI2zEf4OhDZvxg88xQIjr+HSFrM870vjMpVdh6zLCqVHTxDQsleR6iDvfXC4wQTw7ngvJWd87g74XC5GclQC4lGR83NrpPkDkmBG6OgrRN6S31jHZJ6t1hrOZtPOR7El0QLIJKUeKH8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749451806; c=relaxed/simple; bh=6yy7uWYBmrpwoqPT7FTXXF937NeAXtOiGTHzyLC+6Wk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=e8ALlDrUCkdwhxD1PLGmPflev4TjGBElMOlekfPiHweZieRYbGnCl8ffua7dW8hGYewMRc/hgXde+uSCKsYSuqrAEyUH39xRUZZCYd/QrNyuIMTd06F2I0mRcg/Jcb3ssCjfXT7H+hm54pAda/TxmM5YCrtudljNjINYnX+XHNg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-681ff7000002311f-5c-6846841883c9 Date: Mon, 9 Jun 2025 15:49:55 +0900 From: Byungchul Park To: willy@infradead.org, netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, kuba@kernel.org, almasrymina@google.com, ilias.apalodimas@linaro.org, harry.yoo@oracle.com, hawk@kernel.org, akpm@linux-foundation.org, davem@davemloft.net, john.fastabend@gmail.com, andrew+netdev@lunn.ch, asml.silence@gmail.com, toke@redhat.com, tariqt@nvidia.com, edumazet@google.com, pabeni@redhat.com, saeedm@nvidia.com, leon@kernel.org, ast@kernel.org, daniel@iogearbox.net, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, vishal.moola@gmail.com Subject: Re: [PATCH net-next 0/9] Split netmem from struct page Message-ID: <20250609064955.GA57249@system.software.com> References: <20250609043225.77229-1-byungchul@sk.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250609043225.77229-1-byungchul@sk.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0iTYRTHe/Ze9joaPK2sJ5XKaVSWmmF1PkgJWb5BRiAU1Qdd+dJGOmPe g0Jz3cxLmVHOSRNR5wUWS+fsIjbFaQWJZcxqTbQrmF00M9f1VSK//fifP79zPhyOUpxl/DiN Nl3QaVXJSlZGyz7Mrwol+h3q9QMjwWC0NLHQOJUNdUN2BowNNgQT359LYbzLyUJ11SQFxkd6 Gr5apil43T0sBU/tGxrunG2lYLikh4UivZeCU3azBPpsxQyUTddQ0Jo7JIXHt4wsvGz6zcAb RxENvYZ6GjzF0dBtWgyTD0YRdFlaJTBZWMnC5X4TCyN6D4L+zmEaKvKKEVjaXQx4p4xsdCDf XD8o4dsMbilvsmbwN80hfIGrn+KtDedZ3vqlVMq/eHqH5XuueWm+zT4u4Yvyx1j+8+tnNP+x fYDlLc0DNP/Q1CXlx63L9uADsqgkIVmTKejCtyTK1IXvs465IftTnwvlItu6AuTDERxJ8r7Z 6QLEzfCYOVGMaRxMci/opSKzeBVxub5TYmURDidPS/cXIBlH4R6GeK+/Y8TOQryVfHsxwoos x0Cmhs/N5Aq8kTiemKnZfAHpLX9Fi0zhEOL69V4iOinsT+p+cSL64E1kyJUuNnxxEOmwOSXi KoJrONJY3SKdvXgpuWd20RcRNsyxGuZYDf+tJkQ1IIVGm5mi0iRHhqlztJrssMOpKVb09z1q T/w4aEdf+uIdCHNIOV+eeHW7WsGoMtNyUhyIcJRykRx7tqkV8iRVznFBl5qgy0gW0hzIn6OV S+QbJrOSFPiIKl04KgjHBN2/qYTz8ctF6QGlg7dj78e9jVCXBI5ORDy37Yw57RfUUtHvDZ+4 cslfNc/XufddXKpzpU+o32lNfka3M253QLawb2ns9q4blp8ng5/EX86PzHM3Ra6+uX9VeVne 3tKY1KrprOUr1nzV6HZpy4OjDhV3dB5KoKrjK6vbzO6GXQMta71h6tuNdzefCVHSaWpVRAil S1P9AUtQ+nQaAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTcRjG+e+cnZ2NVsdpeVCUmIUhpUkqLxUmWfbvghR9EPuiwx3bUKds aloUcw4sL8tLUK1ZC8lMhYXKNBGLJakZaZo17zIvVMTMvGTOrFZEfvvxvL/n+fTShOQT6UMr VZmcWiVLlVIiUhR7IH8Pq49R7H3j3AomSz0FdSs58HCyhQ+mWiuCxe8jAljo6KSg6v4yAaZe PQlLllUCZl44BDBRPUtCW0EzAY7rXRSU6F0E6FpqePC8spsPfVYDH26sPiCgWTspgIFWEwXj 9T/5MGsrIaHb+IiECUMUvDBvg+Wezwg6LM08WC6upKCi30zBlH4CQf9zBwl38gwILO12PrhW TFSUFDc9GuLhJ8YxATY3ZOHGmiBcaO8ncEPtNQo3fC0X4NF3bRTuuuUi8ZOWBR4uyXdSeH5m mMRz7YMUrvrwhYctTYMkfmXuEJz2OCc6KOdSldmcOiQyUaQo/nghYwxyvvTZkRZZdxcimmaZ MNZZk1iIhDTJ7GC1RXqBmykmkLXbvxNuxYsJYd+VxxciEU0wXXzWde8D3+14MofYb6NTlJvF DLArjqt/cgkTztre1hB/cw+2+/Y06WaCCWLt6x957k2C8WUfrtNuFDIR7KQ9021sZQLYZ9ZO XikSGzeUjRvKxv9lMyJqkZdSlZ0mU6aGB2tSFLkqZU5wUnpaA/r9AdWX18pa0OLAMRtiaCTd JE68eVQh4cuyNblpNsTShNRLzExEKyRiuSz3IqdOT1BnpXIaG/KlSam3+EQclyhhzssyuRSO y+DU/648WuijRa9HRure9yaMr0syjogbQ3WXsuYqJKLeIkMrlyc8c9buRCfvls31aK78CJ8O wIFRxqTY42ve8dEHns5fEE0l7wzzK981eco2NLw/ZrB9+0t/v8g1w3CIv+vwvuqheXnBZt0W 7cLSY12Sp6M1IPmeMq7pk0VdSmXvr4rwkMpVjZelpEYhCw0i1BrZL1SNyB39AgAA X-CFilter-Loop: Reflected On Mon, Jun 09, 2025 at 01:32:16PM +0900, Byungchul Park wrote: > Hi all, I'm so sorry.. I missed to add v5 into the prefix.. Byungchul > In this version, I'm posting non-controversial patches first. I will > post the rest more carefully later. In this version, no update has been > applied except excluding some patches from the previous version. See > the changes below. > > --8<--- > 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. 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. > > The final patch removing the page pool fields will be submitted once > all the converting work of page to netmem are done: > > 1. converting of libeth_fqe by Tony Nguyen. > 2. converting of mlx5 by Tariq Toukan. > 3. converting of prueth_swdata (on me). > 4. converting of freescale driver (on me). > > For our discussion, I'm sharing what the final patch looks like the > following. > > Byungchul > --8<-- > commit 1847d9890f798456b21ccb27aac7545303048492 > Author: Byungchul Park > Date: Wed May 28 20:44:55 2025 +0900 > > mm, netmem: remove the page pool members in struct page > > Now that all the users of the page pool members in struct page have been > gone, the members can be removed from struct page. > > However, since struct netmem_desc still uses the space in struct page, > the important offsets should be checked properly, until struct > netmem_desc has its own instance from slab. > > Remove the page pool members in struct page and modify static checkers > for the offsets. > > Signed-off-by: Byungchul Park > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 32ba5126e221..db2fe0d0ebbf 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -120,17 +120,6 @@ struct page { > */ > unsigned long private; > }; > - struct { /* page_pool used by netstack */ > - /** > - * @pp_magic: magic value to avoid recycling non > - * page_pool allocated pages. > - */ > - unsigned long pp_magic; > - struct page_pool *pp; > - unsigned long _pp_mapping_pad; > - unsigned long dma_addr; > - atomic_long_t pp_ref_count; > - }; > struct { /* Tail pages of compound page */ > unsigned long compound_head; /* Bit zero is set */ > }; > diff --git a/include/net/netmem.h b/include/net/netmem.h > index 8f354ae7d5c3..3414f184d018 100644 > --- a/include/net/netmem.h > +++ b/include/net/netmem.h > @@ -42,11 +42,8 @@ struct netmem_desc { > static_assert(offsetof(struct page, pg) == \ > offsetof(struct netmem_desc, desc)) > NETMEM_DESC_ASSERT_OFFSET(flags, _flags); > -NETMEM_DESC_ASSERT_OFFSET(pp_magic, pp_magic); > -NETMEM_DESC_ASSERT_OFFSET(pp, pp); > -NETMEM_DESC_ASSERT_OFFSET(_pp_mapping_pad, _pp_mapping_pad); > -NETMEM_DESC_ASSERT_OFFSET(dma_addr, dma_addr); > -NETMEM_DESC_ASSERT_OFFSET(pp_ref_count, pp_ref_count); > +NETMEM_DESC_ASSERT_OFFSET(lru, pp_magic); > +NETMEM_DESC_ASSERT_OFFSET(mapping, _pp_mapping_pad); > #undef NETMEM_DESC_ASSERT_OFFSET > > /* > --- > Changes from v4: > 1. Add given 'Reviewed-by's, thanks to all. > 2. Exclude potentially controversial patches. > > Changes from v3: > 1. Relocates ->owner and ->type of net_iov out of netmem_desc > and make them be net_iov specific. > 2. Remove __force when casting struct page to struct netmem_desc. > > Changes from v2: > 1. Introduce a netmem API, virt_to_head_netmem(), and use it > when it's needed. > 2. Introduce struct netmem_desc as a new struct and union'ed > with the existing fields in struct net_iov. > 3. Make page_pool_page_is_pp() access ->pp_magic through struct > netmem_desc instead of struct page. > 4. Move netmem alloc APIs from include/net/netmem.h to > net/core/netmem_priv.h. > 5. Apply trivial feedbacks, thanks to Mina, Pavel, and Toke. > 6. Add given 'Reviewed-by's, thanks to Mina. > > Changes from v1: > 1. Rebase on net-next's main as of May 26. > 2. Check checkpatch.pl, feedbacked by SJ Park. > 3. Add converting of page to netmem in mt76. > 4. Revert 'mlx5: use netmem descriptor and APIs for page pool' > since it's on-going by Tariq Toukan. I will wait for his > work to be done. > 5. Revert 'page_pool: use netmem APIs to access page->pp_magic > in page_pool_page_is_pp()' since we need more discussion. > 6. Revert 'mm, netmem: remove the page pool members in struct > page' since there are some prerequisite works to remove the > page pool fields from struct page. I can submit this patch > separatedly later. > 7. Cancel relocating a page pool member in struct page. > 8. Modify static assert for offests and size of struct > netmem_desc. > > 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 (9): > netmem: introduce struct netmem_desc mirroring struct page > page_pool: rename page_pool_return_page() to page_pool_return_netmem() > page_pool: rename __page_pool_release_page_dma() to > __page_pool_release_netmem_dma() > page_pool: rename __page_pool_alloc_pages_slow() to > __page_pool_alloc_netmems_slow() > 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() > netmem: introduce a netmem API, virt_to_head_netmem() > page_pool: access ->pp_magic through struct netmem_desc in > page_pool_page_is_pp() > > include/linux/mm.h | 12 --- > include/net/netmem.h | 138 ++++++++++++++++++++++---------- > include/net/page_pool/helpers.h | 7 +- > mm/page_alloc.c | 1 + > net/core/page_pool.c | 36 ++++----- > 5 files changed, 117 insertions(+), 77 deletions(-) > > > base-commit: 90b83efa6701656e02c86e7df2cb1765ea602d07 > -- > 2.17.1