JBoss A-MQ shows Producer Flow Control kicks in when large message is sent

Issue

• How do I sent large message to JBoss A-MQ? The average message size is around 4mb, and using the default AMQ 6.3 setup, I use the activemq producer to test it. 1GB heap and 1mb memory will trigger a OOME and pfc, and I think it is related to https://issues.jboss.org/browse/ENTMQ-1090
  Once I increased the heap to 2GB, no more OOME but I still encountered pfc after 453 or 4mb messages [1]. Increasing the memory limit I can avoid that problem, but what I don't understand is why. I thought pfc will be trigger until the kahadb ran out of space, and if memoryLimit is set to 1mb and a 4mb message should have triggered PFC at the first messages but it didn't. Why would I encounter PFC after 453 messages sent? Is there a formula to help guide the memoryLimit?

• The maxExpirePageSize, maxBrowsePageSize and maxPageSize A-MQ Destination Properties policies are not adequately documented. Customer wanted clarification on their use and possible interrelationships.

[1]
2016-11-08 13:47:40,929 | INFO | .0.1:33303@61616 | Queue | 162 - org.apache.activemq.activemq-osgi - 5.11.0.redhat-630187 | Usage Manager Memory Limit (1048576) reached on queue://TEST, size 453. Producers will be throttled to the rate at which messages are removed from this destination to prevent flooding it. See http://activemq.apache.org/producer-flow-control.html for more info.