misc/179824: System (9.1-p4) hangs on heavy ixgbe network traffic with hw.ixgbe.num_queues=6

[lt]

>Number:         179824
>Category:       misc
>Synopsis:       System (9.1-p4) hangs on heavy ixgbe network traffic with hw.ixgbe.num_queues=6
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Jun 21 23:40:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     lt
>Release:        9.1-RELEASE-p4
>Organization:
>Environment:
FreeBSD cache01 9.1-RELEASE-p4 FreeBSD 9.1-RELEASE-p4 #0: Mon Jun 17 11:42:37 UTC 2013     root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64

>Description:
A 6-CPU core 9.1-RELEASE-p4 system equipped with intel 82599EB NIC with hw.ixgbe.num_queues=6 hangs when traffic volume is heavy.

The system hang can be workarounded by setting hw.ixgbe.num-queues=4


>How-To-Repeat:
HW/SW setup - 9.1-RELEASE-p4 with the 82599EB NIC on a 6-CPU core system

Using a nginx webserver and use clients like http_load to stress the 10G network interface. System will hang within 30 seconds.

Hard reboot is required.

>Fix:
change hw.ixgbe.num_queues=4 (or 2) in /boot/loader.conf

>Release-Note:
>Audit-Trail:
>Unformatted: