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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 195D5160005 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 8c5nnais7izmf9ua8g14p6haiu4wr4yq X-HE-Tag: 1746817490-424354 X-HE-Meta: U2FsdGVkX1+2Tl4sX4rT85e0RuPSVopUNq0JYvk/G9j6ebcfjcI+yFAYdG2EsBPEzPcXfrnMe3KNZUAhWK9AZQu0jge/yg1d+LLbU1ZfyfRj3zpQxIry1ymZ1He60/NXPX/hY67JwDTyntlxi8Ag6+MLL/mL28l7DvBCoRgGwwY0MlwGmwsldCA90xz/G69EyY6dqnp0zoZToZ1IPKSKWl8Juj3ehIV1H29dFbI2Tm7pB673jY3qe6AAZrFvBReOgrFh15WajfCPgGl7lGU4apxU72Np6HscKhpX0+r7OrGuTj9ozPTluU1PgTnm2S8EcVk3pw92RJO9fwi1a0RZ2qCNFoc2VTTN2PRQ0TMWC3ut5aZSLHsupNBSGgDxW8LTVetjldMlhEsPPXUyyjVGH13cRU3FscvueTn8hsTdu7bYW0Bhjj0vPIbNTMT+so6vbudWKTjmV+yCkPdGyStcTrQkgZEExF7kpMkXL+6bZQaVqF4b/3fN+ZgHnO7NIPlcpHD1begGtFKHn2uoaBpjeOhCPO5m3PLTGxvG3YusxhWbLWeFIF8nU6KjTyIZ83uhsqHXsNL1pZUoxa9b6IhyLkc2FxSBGN4qNSC+kB+iXkHXRWMVSP7UanCycipEt9x8+ES3ExEQVRyyl/HnH3dvjOgt4PJHSqWlyQnMrgqwx5OQFk+tRT7bVnoJQBr8/4uuhILiLHq9sNlomUHQHFIvQJK7vOTOjzG919PjNb9IaA/GvUaTAVvuzPhedZQisoDhWBHscMBz3F6Y1Abm1cBJvNRgQ3g6IrC7iUhOgLfk85APiNzqxEMK6Qt//Gi+Nyq0c4Mym7tOL8fXR1E0j+LfCkLXRPKACV50701bmzoyPwj+otKSsuzbB4ipGPXVH17iVw5fpsDyTUXjSKEN6Le0DBtscWWlZkxNyhIL3Dpe24V7i2nm8XNsqkG5N2x//bkDfpVzfSEVuT7UC+Yh35s wKK4/9aE HpKftY9+1SNurlAjEzeoul4XTZ6pAHTEwb5svH+BGFj6bCcrJc502vM1e/QoD5fb4OijYUptyAmcKRrkZjaAcrC2o4mq1D/Yup6lg9U6oipQLppzKiKBvZYgxvBmcPn5F1AY2bg94kcSdnyrZalSDf3NtYc6iZOX3I0io80bIya8nGHEsx+SlpwG6nrtCGhttDz16wObzX6OXGWn7qAlb4z7DayUQooc2zhgWC1CIotPh7l9g1x2ikMEsHLs0IxKrKHVHhPmrKlU5O3FqeEai0C8xViCHIv+hnAwbdDbZO0wfJapv9Cz0rHN6s5n63m8I1cjl4J+KU1Vz2fI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, May 9, 2025 at 11:11=E2=80=AFAM Matthew Wilcox wrote: > > On Fri, May 09, 2025 at 10:32:08AM -0700, Mina Almasry wrote: > > Currently the only restriction on net_iov is that some of its fields > > need to be cache aligned with some of the fields of struct page, but > > Cache aligned? Do you mean alias (ie be at the same offset)? > > > What I would suggest here is, roughly: > > > > 1. Add a new struct: > > > > struct netmem_desc { > > unsigned long pp_magic; > > struct page_pool *pp; > > unsigned long _pp_mapping_pad; > > unsigned long dma_addr; > > atomic_long_t pp_ref_count; > > }; > > > > 2. Then update struct page to include this entry instead of the definit= ions: > > > > struct page { > > ... > > struct netmem_desc place_holder_1; /* for page pool */ > > ... > > } > > No, the point is to move these fields out of struct page entirely. > > At some point (probably this year), we'll actually kmalloc the netmem_des= c > (and shrink struct page), but for now, it'll overlap the other fields > in struct page. > Right, all I'm saying is that if it's at all possible to keep net_iov something that can be extended with fields unrelated to struct page, lets do that. net_iov already has fields that should not belong in struct page like net_iov_owner and I think more will be added. I'm thinking netmem_desc can be the fields that are shared between struct net_iov and struct page (but both can have more specific to the different memory types). As you say, for now netmem_desc can currently overlap fields in struct page and struct net_iov, and a follow up change can replace it with something that gets kmalloced and (I guess?) there is a pointer in struct page or struct net_iov that refers to the netmem_desc that contains the shared fields. --=20 Thanks, Mina