L. C. Hsieh created SPARK-57036:
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Summary: Use intrinsic bulk-fill APIs for constant-value
WritableColumnVector methods
Key: SPARK-57036
URL: https://issues.apache.org/jira/browse/SPARK-57036
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 4.3.0
Reporter: L. C. Hsieh
SPARK-57024 fixed the degenerate per-element loops in three bulk-fill
methods (OnHeap.putNulls, OnHeap.putInts(rowId, count, value),
OffHeap.putNulls). The same pattern still exists in six sibling methods:
OnHeapColumnVector:
putBooleans(int rowId, int count, boolean value)
putBytes(int rowId, int count, byte value)
putShorts(int rowId, int count, short value)
putLongs(int rowId, int count, long value)
OffHeapColumnVector:
putBooleans(int rowId, int count, boolean value)
putBytes(int rowId, int count, byte value)
These should use the same Arrays.fill / Platform.setMemory intrinsic
substitutions as SPARK-57024, with the same SET_MEMORY_THRESHOLD=128
fallback in OffHeap for small-count fills (where the setMemory JNI cost
dominates).
Measured on Apple M4 Max + OpenJDK 21.0.8, using a new
WritableColumnVectorBulkFillBenchmark:
OffHeap byte fills (putBytes / putBooleans) at count=4096+:
baseline: ~4,300 M/s (per-byte Unsafe.putByte loop)
patched: ~42,000 M/s (Platform.setMemory, threshold path)
-> ~10x improvement
OnHeap byte fills at small/medium count (8 to 4096):
baseline: loop, partially auto-vectorized by C2
patched: Arrays.fill intrinsic
-> +5-25% improvement at counts <= 4096; saturated at memory bandwidth
for larger counts (where Arrays.fill and the C2-vectorized loop
converge)
OnHeap shorts/longs: small (+1-14%) improvement at small counts,
saturated at memory bandwidth for large counts. Included for consistency
with the byte methods rather than for headline performance gains.
The OffHeap multi-byte fills (putShorts / putInts / putLongs /
putFloats / putDoubles) are NOT in scope: Platform.setMemory is byte-
only and there is no clean intrinsic substitute for multi-byte values
that aren't uniform-byte (the value=0 special case was prototyped under
SPARK-57024 and rejected as offering no measurable gain).
OnHeap putInts is excluded (already fixed in SPARK-57024).
OnHeap putFloats / putDoubles are excluded (already use Arrays.fill).
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