From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.skhynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id CE522226D18; Thu, 26 Jun 2025 06:41:25 +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=1750920093; cv=none; b=XH8eRNZJp+AjmY+1+qUSqFzr/y3UxhbPYG7suP8n30kR4rQ9o20LncNgW2dBG7w2tGJxH8G9mRS9wUsDiGobYxYAfKbJ/TQnAEYH4iqcdBFnZaJFQlB3ufFSMLjJDBcnGfdZ8l/8gPfzKB+k/3SOnpWgTLmnW6ctZlCtEDpa9G8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750920093; c=relaxed/simple; bh=IBU45ngT/QcLkfOFXGQS3B/xyXruqk6nhJNIpi8dvPo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dUFMZ+AWwPKNArEn6+LF8vuqeVYK6+VB2to7a6Uu6UJ+UtKY78nvg6RNiF85micRQvOj2jGwxIHu/Dt9eDo+nKtj1sAIHcYisORw9E2aYZP6c4oDLqJvxrm9FMi4LGkokB5xMvyq98ZV+A73NSL5w6CzHLckwLPGK6vK4zqHJRo= 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-669ff7000002311f-a7-685ceb94fdf3 Date: Thu, 26 Jun 2025 15:41:19 +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, hannes@cmpxchg.org, ziy@nvidia.com, jackmanb@google.com Subject: Re: [PATCH net-next v7 0/7] Split netmem from struct page Message-ID: <20250626064119.GB28653@system.software.com> References: <20250625043350.7939-1-byungchul@sk.com> Precedence: bulk X-Mailing-List: netdev@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: <20250625043350.7939-1-byungchul@sk.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTYRjHefeenXNcTo6zy5sJ1UpCSbtQ9EQR0ZdeKiHqUxeylac2mhqb Li0qdUYkbYVJ2VyxCLelwWKFzkir6bxQpBmuZV5q3S8mZYnTqDxW1Lcf/+fP73k+PDxWnZPH 87qsHNGQpdGrWQWjGIi+lFL2Ybt2YcQ9G+yeqyxUj+SB65lPDvaqGgRfI085GGpqYeHypWEM 9vZiBr55RjG8ag5zUO1Ng37nawZuHa/FED7VyoKleAxDfeQTB0U+tww6aqxyKButxFBb8IyD RzftLPRd/SmH134LA222Kwz0W1dDs2MqDN/7iKDJUyuD4ZMXWDjT6WDhRXE/gs7GMAMVhVYE noaQHMZGxh0VgT5u9Vza+HEQ0xtXnshona2Xow5vLr3uTqYloU5MvVUnWOr9UsrRnuAtlraW jzG0zjckoxbzJ5Z+ftXN0MGGLpZ6bnQx9L6jidsYu1WxMkPU60yiYcGqnQptqy2A99etyCt6 E1eA+lJLUBRPhCXEbBmVlyB+gsu/ZksxIySS+nApKzErzCOhUARLlcnCAhIs3VKCFDwWzCwp 7YowUidOWEPefQ9giZUCEGt1ISexalx5LFj4J48lbedfTvSxkExCP97JJCcWZhDXD16Ko4Sl xB42T1SmCHPInZoWmbSLCD6eXPQG5L9Pnk7uukPMaSTY/tPa/tPa/mkdCFchlS7LlKnR6Zek avOzdHmpu7MzvWj8XZyHv2/zoS8dm/1I4JE6WnktuE2rkmtMxvxMPyI8Vk9Wnl22VatSZmjy D4qG7HRDrl40+tEMnlFPUy4ePpChEvZqcsR9orhfNPydyvio+AK0PCFlE00yPcxACYH7Nv1u xUB9M26c+2h7yqSA/tpeZ3fHoaPsnqePBwaNqvai+auc1tMxb6uIv/3iurS1ceu3mNe4Zz+4 /N6UGMs3BWNcR27vmll/4Vt58t2Xn4dyK2/2eNN9Y2V0lsU10JvUEJvp9D3fsGHjDt3OhKQp qPt4hUvNGLWaRcnYYNT8AtbzIgcqAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTcRjG+Z//2dlxtDpNrYN+m4xASCsq3zDCiuoQFH5IowvU0lMbzgtb iUbJ5jRLcplZ2pywiqy0Wi2bM7yE5mVaGIprrdxkpd0sS81aC8tJUd8envf3/D69NJb4yQha mXGYV2fIVVJKRIq2x+uXln/Yq1jWE5gPJstNCuq+58C1YbsATLU2BFP+F0KYfNRFwZVL0xhM fQUkfLX8wDDS6RNCnXUbeGtGSWgqasDgO9NNQUlBAEOz/5MQ8u3XCWivdgjgqc0ggPIfVzE0 aIeFMPDARIHn5i8BjLaVkOAw3iDBa0iATvMimO4dQ/DI0kDA9OlqCs71myl4VeBF0N/uI6FK Z0BgaXEJIPB91lHV4REmyLj2sXHM1d94TnCNxiEhZ7Ye4e5dj+aKXf2Ys9aeojjrRJmQe+ls orjuygDJNdonCa5E/4nivoy4SW68ZZDirrz9THCW+kEyUbJbtDaVVymzeXXsuv0iRbexA2c1 xufkvwnVIk9MMaJpllnJVk5lFqMQmmRkbLOvjApmilnCulx+HETCmFjWWbarGIlozOgptmzQ TwaZUGYD++5nBw5mMQOsoU4nDGbJrLLQqfvTL2QdF1/P8ZiJZl0z74igEzOR7LUZOliHMKtY k08/h4QzUexDWxdRisTG/9bG/9bGf2szwrUoTJmRnS5XqlbFaNIUuRnKnJiUzHQrmn2ImuM/ z9rR1MCWNsTQSDpPfMe5RyERyLM1ueltiKWxNEx8IW63QiJOlece5dWZ+9RHVLymDUXSpHSx eOtOfr+EOSQ/zKfxfBav/nsl6JAILUqoQaXvN3n7+mxJ90NjI+/nKZ1g92xMlqwYV3oLK2S3 n8WnHLLkB9yOAV0aHpyYCe/9eH7NpsQoxb6i1rxYWUtqlv0EDLWOxHh5jXRsJT5z98CKx3fX h95DrLop9+OxWxtkcSdH3dRRg64nuSJi4UHtgs2rd+StT3J/e5J4eY+U1Cjky6OxWiP/DaLH RgQMAwAA X-CFilter-Loop: Reflected On Wed, Jun 25, 2025 at 01:33:43PM +0900, Byungchul Park wrote: > Hi all, > > In this version, I'm posting non-controversial patches first since there To Jakub and net folks, I believe v7 doesn't include any controversial patches. It'd be appreciated to lemme know if any. Byungchul > are pending works that should be based on this series so that those can > be started shortly. I will post the rest later. > > 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. > 4. converting of freescale driver. > > 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 v5 (no actual updates): > 1. Rebase on net-next/main as of Jun 25. > 2. Supplement a comment describing struct net_iov. > 3. Exclude a controversial patch, "page_pool: access ->pp_magic > through struct netmem_desc in page_pool_page_is_pp()". > 4. Exclude "netmem: remove __netmem_get_pp()" since the API > started to be used again by libeth. > > Changes from v5 (no actual updates): > 1. Rebase on net-next/main as of Jun 20. > 2. Add given 'Reviewed-by's and 'Acked-by's, thanks to all. > 3. Add missing cc's. > > 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 (7): > 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() > 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() > > include/net/netmem.h | 130 ++++++++++++++++++++++++++------ > include/net/page_pool/helpers.h | 7 +- > net/core/page_pool.c | 36 ++++----- > 3 files changed, 124 insertions(+), 49 deletions(-) > > > base-commit: 8dacfd92dbefee829ca555a860e86108fdd1d55b > -- > 2.17.1