The agent DmaQueueMonitor provides visibility into packets coming up to the CPU via CPU queues. Packets are continuously sampled on monitored queues and kept available for reporting when a CPU congestion event occurs. When a queue that leads to CPU processing is congested a PCAP file may be created from the sampled packets that were captured from before and after the congestion event.  The PCAP file is written to the file system for off-line examination.