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I have a implementation where the hardware dispatches 300 packets every second to a host application through DMA transfer and then to the host application's message queue.

When packets are sent at high rate to the app, I see that the app is not receiving one or two packets like this. When I use tcpdump, I see that all packets are posted to the host. But how do i know whether where the packet was dropped? Using debug prints will consume CPU usage and not be easy as well.

Can I find out how many messages that I received on that message queue? Using ipcs -q commmand does not list anything.

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SysV messages queues are small by default, on my system ipcs -l displays:

$ ipcs -l
[...]
------ Messages: Limits --------
max queues system wide = 7890
max size of message (bytes) = 8192
default max size of queue (bytes) = 16384

The corresponding sysctl entries being:

kernel.msgmni = 7890
kernel.msgmax = 8192
kernel.msgmnb = 16384

Depending on how big the messages are, you might hit some of these limits.

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