netudima commented on code in PR #4707:
URL: https://github.com/apache/cassandra/pull/4707#discussion_r3036931463
##########
src/java/org/apache/cassandra/db/ReadResponse.java:
##########
@@ -239,9 +244,15 @@ private LocalDataResponse(UnfilteredPartitionIterator
iter, ColumnFilter selecti
private static ByteBuffer build(UnfilteredPartitionIterator iter,
ColumnFilter selection)
{
- try (DataOutputBuffer buffer = new DataOutputBuffer())
+ // Size output buffer to 10% above the moving average to absorb
minor variance and limit rebuffering.
+ double bufferSizeEstimate =
Double.isNaN(estimatedResponseBytes.get()) ? 128 : estimatedResponseBytes.get();
Review Comment:
nit: better to extract estimatedResponseBytes.get() to a local variable, to
avoid an additional volatile read and longBitsToDouble invocation
##########
src/java/org/apache/cassandra/db/ReadResponse.java:
##########
@@ -239,9 +244,15 @@ private LocalDataResponse(UnfilteredPartitionIterator
iter, ColumnFilter selecti
private static ByteBuffer build(UnfilteredPartitionIterator iter,
ColumnFilter selection)
{
- try (DataOutputBuffer buffer = new DataOutputBuffer())
+ // Size output buffer to 10% above the moving average to absorb
minor variance and limit rebuffering.
+ double bufferSizeEstimate =
Double.isNaN(estimatedResponseBytes.get()) ? 128 : estimatedResponseBytes.get();
+ int initialBufferSize = (int) (bufferSizeEstimate * 1.1);
+
+ try (DataOutputBuffer buffer = new
DataOutputBuffer(initialBufferSize))
{
UnfilteredPartitionIterators.serializerForIntraNode().serialize(iter,
selection, buffer, MessagingService.current_version);
+ estimatedResponseBytes.update(buffer.position());
+
return buffer.buffer();
Review Comment:
what is about buffer.buffer(false) here to avoid ByteBuffer duplication and
save a bit more allocations?, taking in account that DataOutputBuffer is not
reused here
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