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 3009D2EAE3; Thu, 29 May 2025 03:29:09 +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=1748489357; cv=none; b=fuxz/u3SUQ5SkdlAar2T/yV1xQuKZxsHTVpP5K52IbF7PSgi1T3zyhtGJ7oqTvVpID2bsX7olMJAhtBRGu+gKnV1BLbTYcGPY6EnVKrQlUbWbsdDLLA08tpi/whXdanxXXv5PbdIUnsfukQHl580ptGFPyu9RgF8mRMtM+GjGBU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748489357; c=relaxed/simple; bh=IUxEdRG+ZYpiSQ6ECtVtnjnubZIa5EDRVhpJpvsRhsU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TkGEG8tXKf+b9wmPUh7KONQc/nGcdgOD1aTOBOekX25MabX32lKdPrSVH6IQYNiypwAzwbtxRdsVOBMyq/UQJCfimq/QjtuEYWrgoCeN8FS2n706QjYUfZIbNa8x/TfQmm/by1kuLj1WcLJC7FWgqT6zusWy4mRLxNJN03QauH4= 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-22-6837d484f185 Date: Thu, 29 May 2025 12:29:03 +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, anthony.l.nguyen@intel.com Subject: Re: [RFC v3 00/18] Split netmem from struct page Message-ID: <20250529032903.GA14480@system.software.com> References: <20250529031047.7587-1-byungchul@sk.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20250529031047.7587-1-byungchul@sk.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02SbUhTYRTHe+69u7sbrm7L6ikhZRGBkGYveqIy6dNDFAT5xYpq5K2N5hxb vkUvthRp+JaV1DSaSU5nsbLS+ZKoiRkWybKxzFJ0aoYW5QtTy3ITqW8/zvmf3zkfDkfL80Rr ObX2rKDXKjUKVspIxwJKNmV2Rak2192kodj+gIVKbypY+xwiqO/0UlBsq0YwMf1RDOOtL1ko LZmaj73NYGDSPkPDYFu/GHrLhhhoyKqhoT+vnYWcjFkajI5yCjqrc0VwY+Y+DTXpfWJ4V1fM wucHf0Qw1JLDwCtzBQO9uTHQZlkFUx2jCFrtNRRMZd9h4brTwsJARi8C54t+Boou5yKwN7pF MOstZmMU5GnFB4rUmj+JiaUqiTwpDyWlDSMUMbmdNKmyXWVJ1c8CMelxNbCk/dYsQ2od4xTJ ufKNJT8GuxnyvfE9S+xP3zPktaVVfHD5YemueEGjThb04dEnpKohr0SXFZ360OFi0tG1zSYk 4TC/DZdnD4gX2ftpgPIxw2/Ao4WZIh+z/Ebsdk/TJsRxgXw4dhXEmZCUo3mPCM+W5PnzK/gd uK2jlPGxjAdcb/von5XPO2+bmtmF+nL86rbHn6H5UOyeG6F8TpoPwtY5zleW8Ntx4ZNCv3Il vx43Vb+kfLswX8Fha+Y4vXDnGtxc7mbyEW/+T2v+T2v+p7Ug2obkam1yglKt2RamStOqU8NO JiZUofk3Kbvw64gD/ew81IJ4DikCZO0oSiUXKZMNaQktCHO0IlBm3BOpksvilWnnBH3icX2S RjC0oCCOUayWbZlKiZfzp5VnhTOCoBP0i12Kk6xNR/at+c92zTSfKoi0DW+/99hl6HZOxkYt K6T2hBgfvQlRXtz/+Nu6YKcnE+2tfNu2z9MUf6LU9Mh6aVVKcFyArmly6SHPkt13a4ICuw/Q 2pDa52O6iiid5zyZ6fh6tKtLUlQ3atlSORrxpWdlNHVwhebWcOyx39Rk0vRE7M4Nv40lcQrG oFJGhNJ6g/IvoUnNhCIDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTcRjG+Z/bjqPR6eTlVBQ0SUNSE1JfKewGebogfirKDzny1IZzxqai RWW6MFfOtJRaKyaHvKWspuimpjXNFD8kK8e6mGYqBXa1ZLqwmhH57eF5n9/v00vj7FdiNa3S ZAtajUItp6SENHlrUaT+ebxyc4klDMzWRgruevOgdsxOQseQFwNzQyuC73OvJDDT+4QCsXoW B/NTPQE/rPM4TPaNS2C0ZoqAzuI2HMbL+iko1ftwKLTXYdBza4CEoVYjCdfm7+DQVjAmgWft ZgreNP4iYcpZSsCAqZ6AUeMO6LMEw+zgNIJeaxsGs5dvUXDVZaHgnX4UgatnnICb540IrF0e EnxeM7UjlG+pf4HxDtOIhLfYcvjmughe7PyA8QaPC+dtDSUUb/tWIeFfuzspvv+6j+Ad9hmM Ly36RPFfJ18S/OeuYYoX33/BeGvLMJHCHpFuSxfUqlxBG52YJlVOeQNOFifmNdndRAEq32xA ATTHbOG8I+8wfyaYDdx01QXSnykmnPN45nADoulAJppzVxw2ICmNMxMk56suW9yvZBK4vkGR 8GcZA1xHw6tFlv3jvGF4RP3tV3ADNyYWNzgTwXkWPmB+J86s4WoXaH8dwMRyVc1Vi8ogJpR7 2PoEu4JkpiW0aQlt+k9bEN6AAlWa3EyFSh0bpctQ5mtUeVHHsjJt6M8j1Jz5WW5H358lORFD I/kyWT+KV7KkIleXn+lEHI3LA2WF2+OUrCxdkX9K0GYd1eaoBZ0TraEJeYhs3yEhjWVOKLKF DEE4KWj/XTE6YHUBaqspJoMrTWRL4WT3rjJj7/paR0/Squ79Ce6DJZc2Kefikitz0bqsj6LD 1/S2/YoYnJlq/DLOLZ8udzcmRKqGo00zEzEHXGd3W1ins+ucZPvCvdIHUclYkHlCpggpOC2G 58XtvH1RLx6nwjam9p6P2buWTdo7G5gSkvj49P09LjmhUypiInCtTvEbooWcCQQDAAA= X-CFilter-Loop: Reflected On Thu, May 29, 2025 at 12:10:29PM +0900, Byungchul Park wrote: > 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. > > 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. +cc Tony Nguyen +cc Tariq Toukan Byungchul > 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 86be39ea488df859cff6bc398a364f1dc486f2f9 > 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 56d07edd01f9..5a7864eb9d76 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -119,17 +119,6 @@ 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 9e4ed3530788..e88e299dd0f0 100644 > --- a/include/net/netmem.h > +++ b/include/net/netmem.h > @@ -39,11 +39,8 @@ 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 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 (18): > netmem: introduce struct netmem_desc mirroring struct page > 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_netmem_order() > 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 > 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 > netmem: introduce a netmem API, virt_to_head_netmem() > mt76: use netmem descriptor and APIs for page pool > page_pool: access ->pp_magic through struct netmem_desc in > page_pool_page_is_pp() > > drivers/net/ethernet/mellanox/mlx4/en_rx.c | 48 +++--- > drivers/net/ethernet/mellanox/mlx4/en_tx.c | 8 +- > drivers/net/ethernet/mellanox/mlx4/mlx4_en.h | 4 +- > drivers/net/netdevsim/netdev.c | 19 +-- > drivers/net/netdevsim/netdevsim.h | 2 +- > drivers/net/wireless/mediatek/mt76/dma.c | 6 +- > drivers/net/wireless/mediatek/mt76/mt76.h | 12 +- > .../net/wireless/mediatek/mt76/sdio_txrx.c | 24 +-- > drivers/net/wireless/mediatek/mt76/usb.c | 10 +- > include/linux/mm.h | 12 -- > include/net/netmem.h | 145 +++++++++++++----- > include/net/page_pool/helpers.h | 7 +- > mm/page_alloc.c | 1 + > net/core/netmem_priv.h | 14 ++ > net/core/page_pool.c | 101 ++++++------ > 15 files changed, 239 insertions(+), 174 deletions(-) > > > base-commit: d09a8a4ab57849d0401d7c0bc6583e367984d9f7 > -- > 2.17.1