Re-introduce double-mapping for non off-heap case #21107
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amicic
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Feb 11, 2025
| @@ -281,12 +284,47 @@ MM_VLHGCAccessBarrier::jniGetPrimitiveArrayCritical(J9VMThread* vmThread, jarray | |||
| *isCopy = JNI_FALSE; | |||
| } | |||
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|
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| if (alwaysCopyInCritical || !indexableObjectModel->isInlineContiguousArraylet(arrayObject)) { | |||
| if (alwaysCopyInCritical) { | |||
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To make eventual removal of double mapping easier we could do this (just thinking loud, don't do it yet)
#if defined(J9VM_GC_ENABLE_DOUBLE_MAP)
if (alwaysCopyInCritical) {
#else /* defined(J9VM_GC_ENABLE_DOUBLE_MAP) */
if (alwaysCopyInCritical || !indexableObjectModel->isInlineContiguousArraylet(arrayObject)) {
#endif /* defined(J9VM_GC_ENABLE_DOUBLE_MAP) */
amicic
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Feb 11, 2025
| /* alwaysCopyInCritical or discontiguous (including 0 size array) */ | ||
| copyArrayCritical(vmThread, &data, arrayObject, isCopy); | ||
| } else if (indexableObjectModel->isVirtualLargeObjectHeapEnabled() && !indexableObjectModel->isDataAdjacentToHeader(arrayObject)) { | ||
| /* off heap enabled and not adjacent */ | ||
| data = (void *)indexableObjectModel->getDataPointerForContiguous(arrayObject); | ||
| } else if (!indexableObjectModel->isInlineContiguousArraylet(arrayObject)) { | ||
| /* an array having discontiguous extents is another reason to force the critical section to be a copy */ | ||
| #if defined(J9VM_GC_ENABLE_DOUBLE_MAP) |
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in the light of the previous comment, then this ifdef could be just above
else if (!indexableObjectModel->isInlineContiguousArraylet(arrayObject)) {
end its matching endif should be just after the final
{
copyArrayCritical(vmThread, &data, arrayObject, isCopy);
}
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Along with new off-heap feature, double-mapping has been removed (off-heap can cover all of double-mapping cases with better performance), but in case enabling off-heap could not be set as default, re-introduce double-mapping as alternative backup. 1, double mapping is still part of array Discontiguous layout 2, no share code between off-heap and double-mapping Signed-off-by: lhu <[email protected]>
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Along with new off-heap feature, double-mapping has been removed (off-heap can cover all of double-mapping cases with better performance), but in case enabling off-heap could not be set as default, re-introduce double-mapping as alternative backup.
1, double mapping is still part of array Discontiguous layout
2, no share code between off-heap and double-mapping