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Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v6 3/3] io_uring: enable per-io hinting capability Content-Language: en-US To: Pavel Begunkov , Hannes Reinecke , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, martin.petersen@oracle.com, brauner@kernel.org, viro@zeniv.linux.org.uk, jack@suse.cz, jaegeuk@kernel.org, bcrl@kvack.org, dhowells@redhat.com, bvanassche@acm.org Cc: linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-block@vger.kernel.org, linux-aio@kvack.org, gost.dev@samsung.com, vishak.g@samsung.com, javier.gonz@samsung.com, Nitesh Shetty From: Kanchan Joshi In-Reply-To: Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA02Tf1DTZRzH7/nuyzYo3NcJ8UCezVXegYFbwXzwQEyJ+wqeoV53FiEt9uXH bWxrP0Cgu8gOyl0OGYY0EEwpYXJ4DAQGA71JN1H5kQQBDV0xSuCGAXYlBLQxIv97PZ/P+33v 5/N57mHS2GWMIGamVEUppEIJl+6Dt9wKDgl9Z9OTNN5tPQtVGloAujpeTEealWYczdyaB6js j6c0NHtqCUejN00YMl/SYaju6vcYmi3sw1HF+c8w5Limp6EJ2wID6SzDAJ0rOwVQ59hOZO7s wVH1d5MMdMW6gqGWpWoaaph5jKP+ZasX6tdXMvYFkIM/JpAm/TiD7H/QiJODvWrSaDhNJ43z OgbZVPMJ2TFaQCfnJsdw8nHXEJ3UNhsAee9it6t5N59cMG4jjQ4nlsh6TxyVQQlFlIJDSVNl okxpejQ34VjKgZQIAY8fyo9Eu7kcqTCLiubGHkoMjcuUuHbA5WQLJWpXKVGoVHJ37Y1SyNQq ipMhU6qiuZRcJJGHy8OUwiylWpoeJqVUe/g83usRLuEH4ozZykeYvIR50jltoheARroGeDMh EQ6nJ0cYbmYTHQA2n35FA3xcPA9gZ3UTtnFwtmoYG47yy7inYQKwR9u3bncCWDGb7GZfYi+c LDhHczNOvAqHp/6me+qbYc/XDtzN/sSHcHGoErh5CxEHmyr6vdxMIwLgmKN6LdmPMGHw9+WH dPeBRqwC+FWdwaViMulEMBwoVbvRm4iGc/YTHu9LsNVZSXPLIXHDGzospZjn1rHQbm/GPbwF Tlub16cJglPFResshvZf7euaj2Fbk9bLwzGw4J+RtViaK/Za+y5P1iZ4ZsmBucuQ8IVfFLE9 6u3wgW5y3RkAfymv8fJISKhZPuxZ230M6qYasbOAo39mK/pnptc/M43+/+CLADeAQEquzEqn UiPkfCmVs/HcqbIsI1j7ICGxbWCkeiXMAjAmsADIpHH9fHWjc2lsX5EwN49SyFIUagmltIAI 1/OU0IL8U2WuHyZVpfDDI3nhAoEgPPINAZ8b4DtTeEHEJtKFKkpMUXJK8Z8PY3oHFWDPr34e efd624HzXBtrtWX5uslywvnbRM3TrbJs0p6fPWC9uZg0ZDOHmi0Nmi8f2pNfCNhzKHfHQved Ny//FdpRP/Hn23NHqnKOaI/Xq80/JwR+GtX1TVVR1ftgoEXbvhI3ulj6shcLTxhOHjLyrqjr XsyLqt3fwW+focyHbfPlTxrz7MYLtuAYa28WK95vlX20py3wUq6O+e3x2nf9WfcT2IzsnO3i sJKF27263UofwbYbkj4+ETNm08RSE0kN8Zoigah1q+FMzXh+ak7XkvZk0sGDZfU7jg7WxFGF jyLFzxXv3CwpP1b5U0h3oJVzJ62PN3LvtfiPbEv794W8VWsK+yGQiyszhPwQmkIp/Bd5Uipy qQQAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrIIsWRmVeSWpSXmKPExsWy7bCSnG4w35c0gxc3rCzmrNrGaLH6bj+b Rde/LSwWrw9/YrSY9uEns8W7pt8sFjcP7GSy2LNoEpPFytVHmSzetZ5jsZg9vZnJ4sn6WcwW j+98ZreYdOgao8WUaU2MFntvaVvs2XuSxWL+sqfsFsuP/2Oy2PZ7PrPFutfvWSzO/z3OanF+ 1hx2B3GPy1e8PXbOusvucf7eRhaPy2dLPTat6mTz2PRpErvH5iX1HrtvNrB5fHx6i8Xj/b6r bB59W1YxepxZcAQoebra4/MmOY9NT94yBfBHcdmkpOZklqUW6dslcGW8m/OCqWAiR8XbVzvZ Ghg3snUxcnJICJhIvJqxmKWLkYtDSGA7o8SfXXNZIRLiEs3XfrBD2MISK/89Z4coes0o0XRq Mlg3r4CdxNOGKcwgNouAqsS1lz+g4oISJ2c+YQGxRQWSJPbcb2QCsYUF3CQ2zz4PtoAZaMGt J/OZQIaKCOxkkvi48T8biMMs8J9RouPYMiaIdZeYJHa93QCU4eBgE9CUuDC5FMTkFLCV+Pgg DmKQmUTX1i5GCFteYvvbOcwTGIVmIbljFpJ9s5C0zELSsoCRZRWjaGpBcW56bnKBoV5xYm5x aV66XnJ+7iZGcKrQCtrBuGz9X71DjEwcjIcYJTiYlUR4J938mCbEm5JYWZValB9fVJqTWnyI UZqDRUmcVzmnM0VIID2xJDU7NbUgtQgmy8TBKdXAtGty91rZVe5KTw30j9rtT5U90HPz0buu I1u55tobHwuyyKmdd4VhWvP1rz9+WLO73TH4v/O5cvSMKWtkub1UZTae4+jWOr4gyY35iekh YQ2lrUFL5zL9zNryWrdU1KWIffO67WoMpQtEP3JPaWx8YzTDsKnJ8olqVtgcnbBvwVYL20zO r/nXsD5c535PaaF0dxun9QuR2Y9vVzWeePDfj8v1BXMiT73B5e8v9r/UuN75fpJoq/bCIl2e 617qXBm/PPndHsw8+TV86uppvWuqFba+2b/yNkOE8oHrwU6Psz7naGQFp/9b/e349F6u3ILV 7zYvVuP89zp7sWVYhcn14wxBqXILZeI7bh345/34sBJLcUaioRZzUXEiAE9puQyEAwAA X-CMS-MailID: 20240925132124epcas5p1cc362b7e5fec64e41bde11aec1ab9ea5 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" CMS-TYPE: 105P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20240924093257epcas5p174955ae79ae2d08a886eeb45a6976d53 References: <20240924092457.7846-1-joshi.k@samsung.com> <20240924092457.7846-4-joshi.k@samsung.com> <28419703-681c-4d8c-9450-bdc2aff19d56@suse.de> <678921a8-584c-f95e-49c8-4d9ce9db94ab@samsung.com> On 9/25/2024 5:53 PM, Pavel Begunkov wrote: > On 9/25/24 12:09, Kanchan Joshi wrote: >> On 9/25/2024 11:27 AM, Hannes Reinecke wrote: > ... >> As it stands the new struct will introduce >>> a hole of 24 bytes after 'hint_type'. >> >> This gets implicitly padded at this point [1][2], and overall size is >> still capped by largest struct (which is of 16 bytes, placed just above >> this). > > For me it's about having hardly usable in the future by anyone else > 7 bytes of space or how much that will be. Try to add another field > using those bytes and endianess will start messing with you. And 7 > bytes is not that convenient. > > I have same problem with how commands were merged while I was not > looking. There was no explicit padding, and it split u64 into u32 > and implicit padding, so no apps can use the space to put a pointer > anymore while there was a much better option of using one of existing > 4B fields. How would you prefer it. Explicit padding (7 bytes), hint_type as u16 or anything else?