Optimizing multi-source byte range reading in JSON reader #15396
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shrshi
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feature request
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…byte-range-improvement
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| datasource::owning_buffer<rmm::device_uvector<char>> outdata(std::move(outbuf)); | ||
| std::swap(indata, outdata); |
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This looks like it's significant, but I didn't grasp it.
What's the advantage of swapping in place over, say, assigning to indata?
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My reasoning here was that after the RMM buffer in indata datasource has been normalized, we can discard the buffer. Rather than copying outdata to indata with the implicitly generated copy assignment operator in owning_buffer, I thought swapping it would be faster.
cpp/src/io/json/read_json.cu
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| // of subchunks. | ||
| size_t buffer_size = | ||
| reader_compression != compression_type::NONE | ||
| ? total_source_size * compression_ratio + 4096 |
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Why are we adding 4096? Is that for headers?
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Yes, 4096 is for the headers. I've used the uncompressed buffer size estimate from
cudf/cpp/src/io/comp/uncomp.cpp
Line 361 in 064dd7b
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Would be nice to have this guess defined instead of a hard-coded value. I'm ok either way though.
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…byte-range-improvement
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Description
This piece of work seeks to achieve two goals - (i) reducing repeated reading of byte range chunks in the JSON reader, and (ii) enabling multi-source byte range reading for chunks spanning sources.
byte_rangeoption is used inread_json#15185 to reduce the repeated reading of follow-on chunks while searching for the end of the last row in the requested chunk. After the requested chunk, the following chunks are divided into subchunks, and read until the delimiter character is reached.Visualization of the performance improvement with this optimization
Checklist