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Uses 128 bytes padding to prevent false-sharing #191

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Sep 24, 2024
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Uses 128 bytes padding to prevent false-sharing #191

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14 changes: 8 additions & 6 deletions src/main/java/org/jboss/threads/EnhancedQueueExecutor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -333,16 +333,18 @@ private static final class RuntimeFields {
// guess
cacheLine = 64;
}
// cpu spatial prefetcher can drag 2 cache-lines at once into L2
int pad = cacheLine > 128 ? cacheLine : 128;
int longScale = unsafe.arrayIndexScale(long[].class);
int objScale = unsafe.arrayIndexScale(Object[].class);
// these fields are in units of array scale
unsharedObjectsSize = cacheLine / objScale * (numUnsharedObjects + 1);
unsharedLongsSize = cacheLine / longScale * (numUnsharedLongs + 1);
unsharedObjectsSize = pad / objScale * (numUnsharedObjects + 1);
unsharedLongsSize = pad / longScale * (numUnsharedLongs + 1);
// these fields are in bytes
headOffset = unsafe.arrayBaseOffset(Object[].class) + cacheLine;
tailOffset = unsafe.arrayBaseOffset(Object[].class) + cacheLine * 2;
threadStatusOffset = unsafe.arrayBaseOffset(long[].class) + cacheLine;
queueSizeOffset = unsafe.arrayBaseOffset(long[].class) + cacheLine * 2;
headOffset = unsafe.arrayBaseOffset(Object[].class) + pad;
tailOffset = unsafe.arrayBaseOffset(Object[].class) + pad * 2;
threadStatusOffset = unsafe.arrayBaseOffset(long[].class) + pad;
queueSizeOffset = unsafe.arrayBaseOffset(long[].class) + pad * 2;
}
}

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