increasing 'requests for jumbo clusters denied'

[Ihsan Junaidi Ibrahim]

Hi,

I'm on 9.0-RELEASE-p3 and have had a number of instances where my igb0 network connectivity locked up under heavy load.

I've had another em1 device which I used for side-band access which does not have as much load as my primary igb0 device.

I've read previous cases of this but can't seem to find any fitting solutions.

I've tried increasing mbufs and jumbo mbufs:
nsv01-kul:ihsan $ sysctl -a | grep nmb
kern.ipc.nmbjumbo16: 3200
kern.ipc.nmbjumbo9: 25600
kern.ipc.nmbjumbop: 12800
kern.ipc.nmbclusters: 262144

but I'm still receiving a lot of 'requests for jumbo clusters denied' stats on netstat -m output.
nsv01-kul:ihsan $ netstat -m
7347/3063/10410 mbufs in use (current/cache/total)
334/2658/2992/262144 mbuf clusters in use (current/cache/total/max)
334/1330 mbuf+clusters out of packet secondary zone in use (current/cache)
1749/1310/3059/12800 4k (page size) jumbo clusters in use (current/cache/total/max)
5116/563/5679/25600 9k jumbo clusters in use (current/cache/total/max)
0/0/0/3200 16k jumbo clusters in use (current/cache/total/max)
55544K/16388K/71933K bytes allocated to network (current/cache/total)
0/0/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters)
0/25154247/0 requests for jumbo clusters denied (4k/9k/16k)
0/0/0 sfbufs in use (current/peak/max)
0 requests for sfbufs denied
0 requests for sfbufs delayed
0 requests for I/O initiated by sendfile
0 calls to protocol drain routines

The server has not locked up yet after increasing the mbufs (been less than 8 hours since increasing this) but can someone enlighten me what could be the causes for jumbo clusters requests being denied although I've increased the 9k jumbo clusters to 25600?

Thanks.

ihsan