perf: tagged-union packed format eliminates serialize for scalar values#55
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perf: tagged-union packed format eliminates serialize for scalar values#55
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Summary of ChangesHello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request significantly enhances the performance of Judy arrays by introducing a specialized packed format for scalar values. Instead of serializing and unserializing every value, common scalar types are now stored directly within a tagged union, leading to faster read and write operations. Complex types gracefully fall back to the existing serialization mechanism, ensuring compatibility while providing a substantial speed boost for frequently used data types. Highlights
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Code Review
This pull request introduces a significant performance improvement for INT_TO_PACKED Judy arrays by creating a fast path for scalar values, avoiding costly serialization and unserialization. The new implementation uses a tagged union to store scalars directly. The changes are well-implemented and accompanied by good test coverage for both the new fast path and the existing fallback mechanism. I have a couple of suggestions to improve maintainability and fix a potential memory issue in an edge case.
Test Results
Benchmark Summary (Judy vs PHP Array)Ratio = Judy / Array. Bold = Judy wins (≤0.95x). Plain = Array is faster/smaller. Time (Write / Read) — Linux
Memory — Linux
Time (Write / Read) — Windows
Memory — Windows
Raw benchmark dataWrite Time — Linux
Read Time — Linux
Memory — Linux
Write Time — Windows
Read Time — Windows
Memory — Windows
Batch & Set Operations BenchmarksBenchmarks for Batch Operations — PHP 8.5 (Linux)Set Operations — PHP 8.5 (Linux)All-Types Comparison BenchmarkSide-by-side comparison of all six Judy types and native PHP array (50K elements, 3 iterations, Linux only). All-Types Benchmark — PHP 8.5 (Linux) |
Replace the opaque serialize-everything judy_packed_value with a tagged union that stores long/double/bool/null/string directly (tags 0–5), falling back to php_var_serialize only for arrays and objects (tag 255). This avoids the serialize/unserialize overhead for the common case where INT_TO_PACKED stores scalar values. Breaking: old serialized INT_TO_PACKED data is incompatible.
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Rebased onto current Both Gemini review items were addressed in
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Summary
php_var_serialize/php_var_unserializeinjudy_pack_value/judy_unpack_valuewith a direct tagged-union struct (judy_packed_value) for the five common scalar types: long, double, true, false, nulluint8_t tag+ union to store values inline; only non-scalar zvals fall back to the serialization path (tag 255)sliceto usejudy_packed_value_size()+memcpyinstead of unpacking and repacking each valueTest plan
tests/packed_scalar_fastpath_001.phpt— long/double/bool/null round-trip through the fastpathtests/packed_complex_fallback_001.phpt— arrays/objects fall back to serialize correctly