About transferMsgByHeap default value

[luoye783]

I’ve noticed that in the broker configuration, transferMsgByHeap defaults to true. This causes the popMessage method to read data from the page cache into the Java heap before sending the response via Netty. If this flag is set to false, responses are sent using a FileRegion instead. The latter approach reduces the number of memory copies; however, in my experience—and confirmed by benchmarks—having it true actually yields better performance. Given that, I’m curious why the default is false: is there some design consideration or special trade-off I’m overlooking?