Avoid serializing I/O requests from Parquet reader - #23823
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WalkthroughThe PR adds ChangesParquet submission policy
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to The PR changes whether Parquet I/O submissions are serialized, while the helper documentation still describes unconditional locking. This could mislead maintainers about concurrency behavior and warrants documentation follow-up, but the change remains mergeable with explicit owner awareness. Suggested reviewers: 🚥 Pre-merge checks | ✅ 3 | ❌ 2❌ Failed checks (2 warnings)
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Full details: Description checkExplanation The description explains the serialization policy, the Parquet reader behavior, the hybrid scan behavior, and the linked issue. Its boolean terminology is somewhat outdated because the implementation now uses an enum policy, but it remains related to the changeset. Full details: Linked Issues checkExplanation The changes satisfy the objective in [ Full details: Out of Scope Changes checkExplanation The pull request includes changes outside [ Resolution Remove unrelated metadata-cache, prepare_dictionaries stream, and apply_retention_mask changes, or explain and link the requirements that justify them. Keep only the I/O submission policy changes and required call-site, binding, documentation, and test updates. ✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In `@cpp/src/io/parquet/io_utils/parquet_io_utils.cpp`:
- Around line 236-237: Update the documentation for read_ranges_to_host to state
that host_read_mutex() is held while scheduling batches only when
serialize_submissions is true; preserve the existing implementation behavior,
including the unlocked path when the flag is false.
- Around line 250-251: Add blocking-datasource unit-test coverage for both
values of serialize_submissions, verifying submission behavior with
serialization enabled and disabled. Add a benchmark that measures both modes
using the existing parquet I/O test and benchmark conventions.
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cpp/include/cudf/io/parquet_io_utils.hppcpp/src/io/parquet/bloom_filter_reader.cucpp/src/io/parquet/io_utils/parquet_io_utils.cppcpp/src/io/parquet/reader_impl_preprocess_utils.cu
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## Summary - Return a deferred future for cache-backed H2D work when `GLUTEN_CUDF_CACHE_H2D_INLINE=1`. - Keep the copy on the waiting caller thread while moving it out of cuDF's process-wide device-read submission critical section. - Add focused coverage using cuDF's public byte-range fetch helper and two independent data sources/streams. ## Motivation [cuDF #22586](NVIDIA/cudf#22586) serializes `device_read_async()` submission through a process-wide mutex. The existing inline cache path performs cache lookup, cache-page traversal, pin retention, and H2D submission before returning a ready future, so all of that work runs while cuDF holds the mutex. Unrelated scan drivers then form a lock convoy. This change returns a `std::launch::deferred` future instead. Creating the future is cheap; cuDF releases its submission mutex before waiting on it, and the actual copy still runs inline on the waiting caller thread. This preserves the intended inline execution model and cache-pin lifetime while restoring concurrency across callers. This is a consumer-side mitigation for [cuDF issue #23799](NVIDIA/cudf#23799). [cuDF PR #23823](NVIDIA/cudf#23823) remains the cleaner owner-side fix; this shim should be re-evaluated once a qualified runtime contains that change. ## Validation - Test-enabled cuDF target build: 1000/1000 targets completed. - Focused tests passed: `directCachePageH2dAvoidsHostStaging` and `deferredCacheH2dDoesNotHoldCudfSubmissionMutex` (2/2). - AWS EMR on EKS, 4 x `g7.8xlarge`, Parquet SF1000 on S3, strict cold Q1-Q22, one iteration per arm. - Same Spark-Gluten, cuDF, configuration, data, and retained cluster; the Velox patch was the only source difference. - Baseline: **132.006 s**, 22/22 execution and same-run semantic-digest checks passed. - Patched: **123.840 s**, 22/22 execution and same-run semantic-digest checks passed. - Delta: **-8.167 s (-6.19%, 1.066x)**; 17/22 queries improved. The recovered 8.167 seconds closely matches the independently isolated 8.068-second `GLUTEN_CUDF_CACHE_H2D_INLINE=1` regression introduced by cuDF #22586. This change addresses that mutex convoy only; it does not claim to eliminate every performance difference between cuDF releases.
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Description
Closes #23799
This PR adds a boolean flag in
parquet_io_utilsto enable serializing (via mutex) I/O submission from callers. The boolean flag defaults totrueenabling serialization for better pipelining between IO and compute.Parquet reader path (libcudf internal) now passes a
falseto this flag reverting its old behavior. Hybrid scan paths remain unchanged.Checklist