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Batch memcpy the last offsets for output buffers of str and list cols in PQ reader #16905

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mhaseeb123
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@mhaseeb123 mhaseeb123 commented Sep 25, 2024

Description

This PR adds the capability to batch memcpy the last offsets for the output buffers of string and list columns in PQ reader. This reduces the overhead from several cudaMemcpyAsync calls when reading wide strings and/or list columns tables. This optimization was found as well as ORC changes were contributed by @vuule. See this comment for performance improvement data and discussion.

Checklist

  • I am familiar with the Contributing Guidelines.
  • New or existing tests cover these changes.
  • The documentation is up to date with these changes.

@mhaseeb123 mhaseeb123 self-assigned this Sep 25, 2024
@github-actions github-actions bot added the libcudf Affects libcudf (C++/CUDA) code. label Sep 25, 2024
@mhaseeb123 mhaseeb123 changed the base branch from branch-24.10 to branch-24.12 September 25, 2024 03:25
@mhaseeb123 mhaseeb123 added 2 - In Progress Currently a work in progress improvement Improvement / enhancement to an existing function non-breaking Non-breaking change cuIO cuIO issue labels Sep 25, 2024
@mhaseeb123 mhaseeb123 changed the title Batch memcpy the last offsets for output buffers of str and list cols in PQ reader 🚧 Batch memcpy the last offsets for output buffers of str and list cols in PQ reader Sep 25, 2024
@vuule vuule self-requested a review September 25, 2024 18:34
@github-actions github-actions bot added the CMake CMake build issue label Sep 26, 2024
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mhaseeb123 commented Sep 26, 2024

Performance Improvements

Summary

The time to write final offsets for STRING and LIST columns via 4 byte H2D memcpys in reader::impl::decode_page_data significantly reduced. The effect is dramatic for wide tables with many string and list cols.

Benchmark Setup

Benchmark name: PARQUET_READER_NVBENCH -b parquet_read_wide_tables
Table properties: data_size = 1GB across num_cols = 1024 (all STRING type), cardinality=0, run_len=16
GPU: NVIDIA RTX 5880 Ada Generation

Profiles (Before = top, After = bottom)

Before: 1024 x cudaMemcpyAsync = 2.393ms
After: 9us for 2 x cudaMemcpyAsync (the two small red bars just before the highlighted region) + 214us for cub::DeviceMemcpy::Batched()

Screenshot 2024-09-25 at 6 30 34 PM

CC @GregoryKimball

@mhaseeb123 mhaseeb123 changed the title 🚧 Batch memcpy the last offsets for output buffers of str and list cols in PQ reader Batch memcpy the last offsets for output buffers of str and list cols in PQ reader Sep 26, 2024
@mhaseeb123 mhaseeb123 marked this pull request as ready for review September 26, 2024 01:02
@mhaseeb123 mhaseeb123 requested a review from a team as a code owner September 26, 2024 01:02
@mhaseeb123 mhaseeb123 added 3 - Ready for Review Ready for review by team and removed 2 - In Progress Currently a work in progress labels Sep 26, 2024
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cool stuff!
Bunch of small suggestions, mostly to polish the new functions

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@mhaseeb123 mhaseeb123 requested a review from a team as a code owner October 1, 2024 01:46
@mhaseeb123 mhaseeb123 removed the request for review from a team October 1, 2024 01:51
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/ok to test

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@vyasr vyasr left a comment

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This is nice!

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/ok to test

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/merge

@rapids-bot rapids-bot bot merged commit 7ae5360 into rapidsai:branch-24.12 Oct 3, 2024
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@mhaseeb123 mhaseeb123 deleted the fea-batch-memcpy-list-str-output-buff-offsets branch October 3, 2024 03:26
@mhaseeb123 mhaseeb123 added 5 - Ready to Merge Testing and reviews complete, ready to merge and removed 3 - Ready for Review Ready for review by team labels Oct 15, 2024
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4 participants