ena(4) tx timeout messages in dmesg

hey there - i have an ec2 instance that i'm using as a nfs server and 
have noticed the following messages in my dmesg buffer:

ena0: Found a Tx that wasn't completed on time, qid 2, index 593. 10 
msecs have passed since last cleanup. Missing Tx timeout value 5000 msecs.
ena0: Found a Tx that wasn't completed on time, qid 2, index 220. 1 
msecs have passed since last cleanup. Missing Tx timeout value 5000 msecs.
ena0: Found a Tx that wasn't completed on time, qid 3, index 240. 1 
msecs have passed since last cleanup. Missing Tx timeout value 5000 msecs.
ena0: Found a Tx that wasn't completed on time, qid 3, index 974. 1 
msecs have passed since last cleanup. Missing Tx timeout value 5000 msecs.
ena0: Found a Tx that wasn't completed on time, qid 2, index 730. 1 
msecs have passed since last cleanup. Missing Tx timeout value 5000 msecs.
ena0: Found a Tx that wasn't completed on time, qid 2, index 864. 10 
msecs have passed since last cleanup. Missing Tx timeout value 5000 msecs.
ena0: Found a Tx that wasn't completed on time, qid 3, index 998. 1 
msecs have passed since last cleanup. Missing Tx timeout value 5000 msecs.


the system is not overly loaded, but does have a steady %25 CPU usage 
and averages around 2MB/sec network throughput (the system serves a 
python virtual-environment to a cluster of data processing systems).

The man page states: "Packet was pushed to the NIC but not sent within 
given time limit.  It may be caused by hang of the IO queue."

I was curious if anyone had any idea if these messages indicate a poorly 
tuned system, or are they just informational.  Looking at the basics 
like mbuf's and other base metrics and the system looks OK from that 
perspective.

thanks!
-pete


-- 
Pete Wright
pete@nomadlogic.org