Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/16403#discussion_r93968567
--- Diff: common/unsafe/src/main/java/org/apache/spark/unsafe/Platform.java
---
@@ -244,6 +257,34 @@ public static void throwException(Throwable t) {
LONG_ARRAY_OFFSET = _UNSAFE.arrayBaseOffset(long[].class);
FLOAT_ARRAY_OFFSET = _UNSAFE.arrayBaseOffset(float[].class);
DOUBLE_ARRAY_OFFSET = _UNSAFE.arrayBaseOffset(double[].class);
+
+ // determine whether double access should be aligned.
+ String arch = System.getProperty("os.arch", "");
+ if (arch.matches("^(arm|arm32)")) {
+ logger.info(
+ "Host platform '{}' requires aligned double access. "+
+ "Creating an aligned buffer for unsafe double reads.",
+ arch);
+
+ // allocate a 2x memory block to ensure buffer used is 8-byte
aligned. Java
+ // objects are always aligned, so we just need to ensure the
offset is aligned
+ // to an 8-byte boundary
+ byte[] heapObj = new byte[16];
+ long offset = BYTE_ARRAY_OFFSET;
+ long bufferSize = 16;
+ for (long i = 0; i < 8; ++i ) {
--- End diff --
Spacing:
```
for (long i = 0; i < 8; i++) {
if ((offset + i) % 8 == 0) {
```
Why a long?
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