Relax mmap read requirement. Improve error message.#781
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rapids-bot[bot] merged 5 commits intorapidsai:branch-25.10from Jul 25, 2025
Merged
Relax mmap read requirement. Improve error message.#781rapids-bot[bot] merged 5 commits intorapidsai:branch-25.10from
rapids-bot[bot] merged 5 commits intorapidsai:branch-25.10from
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kingcrimsontianyu
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madsbk
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Jul 25, 2025
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Looks good, I only have a minor style suggestion
cpp/src/mmap.cpp
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| auto actual_size = size.has_value() ? size.value() : _file_size - offset; | ||
| KVIKIO_EXPECT(actual_size > 0, "Read size must be greater than 0", std::invalid_argument); | ||
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| ss.str(""); |
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Done. Once the C++20 build issue was solved (#749), I'll clean up the repo a bit using std::format.
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### Background Libcudf 25.04 and earlier use `memory_mapped_source` by default. For host read it uses memory mmaped I/O, and for device read it uses standard I/O. Libcudf 25.06 uses standard I/O by default. For host read, `memory_mapped_source` still uses memory mmaped I/O, while the device read is no longer allowed (runtime exception if used). Parquet/ORC readers fall back to the host read + H2D copy to emulate device read for the mapped source. ### This PR Now that the file-backed memory mapping (C++) is supported by KvikIO (rapidsai/kvikio#740), this PR updates libcudf to reinvigorate `memory_mapped_source` using KvikIO's implementation. This re-enables device read and brings performance improvement (e.g. through parallel prefault). ### Notes `memory_mapped_source` is an implementation detail in `datasource.cpp`. Currently testing was conducted on C2C (arm) and PCIe (x86) systems by manually setting `LIBCUDF_MMAP_ENABLED=ON` and running the tests. Refer to rapidsai/kvikio#530 (comment) for benchmark results. ### Dependency This PR depends on KvikIO PR rapidsai/kvikio#781 to fix unit test errors. Authors: - Tianyu Liu (https://github.com/kingcrimsontianyu) - Vukasin Milovanovic (https://github.com/vuule) Approvers: - Vukasin Milovanovic (https://github.com/vuule) URL: #19164
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Aug 27, 2025
…9164) ### Background Libcudf 25.04 and earlier use `memory_mapped_source` by default. For host read it uses memory mmaped I/O, and for device read it uses standard I/O. Libcudf 25.06 uses standard I/O by default. For host read, `memory_mapped_source` still uses memory mmaped I/O, while the device read is no longer allowed (runtime exception if used). Parquet/ORC readers fall back to the host read + H2D copy to emulate device read for the mapped source. ### This PR Now that the file-backed memory mapping (C++) is supported by KvikIO (rapidsai/kvikio#740), this PR updates libcudf to reinvigorate `memory_mapped_source` using KvikIO's implementation. This re-enables device read and brings performance improvement (e.g. through parallel prefault). ### Notes `memory_mapped_source` is an implementation detail in `datasource.cpp`. Currently testing was conducted on C2C (arm) and PCIe (x86) systems by manually setting `LIBCUDF_MMAP_ENABLED=ON` and running the tests. Refer to rapidsai/kvikio#530 (comment) for benchmark results. ### Dependency This PR depends on KvikIO PR rapidsai/kvikio#781 to fix unit test errors. Authors: - Tianyu Liu (https://github.com/kingcrimsontianyu) - Vukasin Milovanovic (https://github.com/vuule) Approvers: - Vukasin Milovanovic (https://github.com/vuule) URL: rapidsai#19164
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cuDF PR rapidsai/cudf#19164 currently has 4 failed unit tests when
LIBCUDF_MMAP_ENABLED=ON:The fix entails code changes on both the KvikIO and cuDF sides.
On the KvikIO side, the
MmapHandle::read()andMmapHandle::pread()methods need to:offsetto be equal toinitial_map_offset(when the read size is 0)This PR makes this change. In addition, this PR adds more detailed error messages when out-of-range exception occurs.