Optimize AbstractListenableFuture Memory Allocations #28
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Problem: If an empty ArrayList has addAll() invoked with a Collection argument that has a size less than 10, the underlying elementData Object[] is still grown to 10 via an Array copy. In the case of AbstractListenableFuture, the number of listeners is often 0 or 1, and AbstractListenableFuture is in the critical path, meaning this behavior causes unnecessary GC pressure for high throughput applications. Therefore, this commit enhances the logic to avoid the construction of the listener copy ArrayList and its iterator if possible, and if not, to use the more efficient constructor vs. addAll().
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Problem: If an empty ArrayList has addAll() invoked with a Collection
argument that has a size less than 10, the underlying elementData
Object[] is still grown to 10 via an Array copy. In the case of
AbstractListenableFuture, the number of listeners is often 0 or 1,
and AbstractListenableFuture is in the critical path, meaning this
behavior causes unnecessary GC pressure for high throughput
applications.
Therefore, this commit enhances the logic to avoid the construction
of the listener copy ArrayList and its iterator if possible, and if
not, to use the more efficient constructor vs. addAll().