unresponsive broker under high load

329 blocked threads, all waiting on:

"Thread-1504284 (ActiveMQ-server-org.apache.activemq.artemis.core.server.impl.ActiveMQServerImpl$5@87a85e1)" Id=1571781 BLOCKED on org.apache.activemq.artemis.utils.SoftValueHashMap@61d63c78 owned by "Thread-1504889 (ActiveMQ-server-org.apache.activemq.artemis.core.server.impl.ActiveMQServerImpl$5@87a85e1)" Id=1572534
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageCursorProviderImpl.getPageCache(PageCursorProviderImpl.java:136)
        -  blocked on org.apache.activemq.artemis.utils.SoftValueHashMap@61d63c78
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageCursorProviderImpl.getMessage(PageCursorProviderImpl.java:115)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl.queryMessage(PageSubscriptionImpl.java:574)
        at org.apache.activemq.artemis.core.paging.cursor.PagedReferenceImpl.getPagedMessage(PagedReferenceImpl.java:101)
        -  locked org.apache.activemq.artemis.core.paging.cursor.PagedReferenceImpl@31fa3436
        at org.apache.activemq.artemis.core.paging.cursor.PagedReferenceImpl.getMessage(PagedReferenceImpl.java:88)
        at org.apache.activemq.artemis.core.server.impl.QueuePendingMessageMetrics.decrementMetrics(QueuePendingMessageMetrics.java:71)
        at org.apache.activemq.artemis.core.server.impl.QueueImpl.decDelivering(QueueImpl.java:3404)
        at org.apache.activemq.artemis.core.server.impl.QueueImpl.postAcknowledge(QueueImpl.java:3021)
        at org.apache.activemq.artemis.core.server.impl.RefsOperation.afterCommit(RefsOperation.java:157)
        -  locked org.apache.activemq.artemis.core.server.impl.QueueImpl@61763b40
        at org.apache.activemq.artemis.core.transaction.impl.TransactionImpl.afterCommit(TransactionImpl.java:546)
        -  locked org.apache.activemq.artemis.core.transaction.impl.TransactionImpl@4e2cbb01
        at org.apache.activemq.artemis.core.transaction.impl.TransactionImpl.access$100(TransactionImpl.java:38)
        at org.apache.activemq.artemis.core.transaction.impl.TransactionImpl$2.done(TransactionImpl.java:304)
        at org.apache.activemq.artemis.core.persistence.impl.journal.OperationContextImpl$1.run(OperationContextImpl.java:236)
        at org.apache.activemq.artemis.utils.actors.OrderedExecutor.doTask(OrderedExecutor.java:42)
        at org.apache.activemq.artemis.utils.actors.OrderedExecutor.doTask(OrderedExecutor.java:31)
        at org.apache.activemq.artemis.utils.actors.ProcessorBase.executePendingTasks(ProcessorBase.java:66)
        at org.apache.activemq.artemis.utils.actors.ProcessorBase$$Lambda$7/888473870.run(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at org.apache.activemq.artemis.utils.ActiveMQThreadFactory$1.run(ActiveMQThreadFactory.java:118)

        Number of locked synchronizers = 1
        - java.util.concurrent.ThreadPoolExecutor$Worker@15eeae7f

Which is waiting on:

"Thread-1504889 (ActiveMQ-server-org.apache.activemq.artemis.core.server.impl.ActiveMQServerImpl$5@87a85e1)" Id=1572534 RUNNABLE
        at io.netty.buffer.WrappedByteBuf.getByte(WrappedByteBuf.java:224)
        at org.apache.activemq.artemis.core.buffers.impl.ChannelBufferWrapper.getByte(ChannelBufferWrapper.java:180)
        at org.apache.activemq.artemis.core.paging.impl.Page.read(Page.java:195)
        at org.apache.activemq.artemis.core.paging.impl.Page.readFromMapped(Page.java:177)
        at org.apache.activemq.artemis.core.paging.impl.Page.read(Page.java:128)
        -  locked org.apache.activemq.artemis.core.paging.impl.Page@64858c85
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageCursorProviderImpl.readPage(PageCursorProviderImpl.java:170)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageCursorProviderImpl.getPageCache(PageCursorProviderImpl.java:151)
        -  locked org.apache.activemq.artemis.utils.SoftValueHashMap@61d63c78
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl$PageCursorInfo.getNumberOfMessages(PageSubscriptionImpl.java:1094)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl$PageCursorInfo.isDone(PageSubscriptionImpl.java:1008)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl$PageCursorInfo.checkDone(PageSubscriptionImpl.java:1083)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl$PageCursorInfo.addACK(PageSubscriptionImpl.java:1063)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl.processACK(PageSubscriptionImpl.java:852)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl.access$1100(PageSubscriptionImpl.java:62)
        at org.apache.activemq.artemis.core.paging.cursor.impl.PageSubscriptionImpl$PageCursorTX.afterCommit(PageSubscriptionImpl.java:1136)
        at org.apache.activemq.artemis.core.transaction.impl.TransactionImpl.afterCommit(TransactionImpl.java:546)
        -  locked org.apache.activemq.artemis.core.transaction.impl.TransactionImpl@476181ad
        at org.apache.activemq.artemis.core.transaction.impl.TransactionImpl.access$100(TransactionImpl.java:38)
        at org.apache.activemq.artemis.core.transaction.impl.TransactionImpl$2.done(TransactionImpl.java:304)
        at org.apache.activemq.artemis.core.persistence.impl.journal.OperationContextImpl$1.run(OperationContextImpl.java:236)
        at org.apache.activemq.artemis.utils.actors.OrderedExecutor.doTask(OrderedExecutor.java:42)
        at org.apache.activemq.artemis.utils.actors.OrderedExecutor.doTask(OrderedExecutor.java:31)
        at org.apache.activemq.artemis.utils.actors.ProcessorBase.executePendingTasks(ProcessorBase.java:66)
        at org.apache.activemq.artemis.utils.actors.ProcessorBase$$Lambda$7/888473870.run(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at org.apache.activemq.artemis.utils.ActiveMQThreadFactory$1.run(ActiveMQThreadFactory.java:118)

        Number of locked synchronizers = 1
        - java.util.concurrent.ThreadPoolExecutor$Worker@6c50069d