Sudden mbuf demand increase and shortage under the load

Vlad Galu dudu at
Sat Jul 10 17:09:14 UTC 2010

On Tue, Feb 16, 2010 at 7:23 PM, Maxim Sobolev <sobomax at> wrote:
> Miroslav Lachman wrote:
>> Can it be related to this issue somehow?
>> It was tested on FreeBSD 8 and high UDP traffic on igb interfaces emits
>> messages "GET BUF: dmamap load failure - 12" and later results in kernel
>> panic.
>> We have not received any response to this report.
> Could be the issue, however in our case there is no panic, just that all
> userland activity in the system ceases for 2 minutes after it reaches
> certain network load level.

Sorry for digging into this old thread, but I'm seeing similar
symptoms with today's RELENG_8 and bge(4) attached to BCM5721, on an UP system.
kern.ipc.nmbclusters is 65536, but what strikes me odd is this:

0/115446003/57722999 requests for mbufs denied (mbufs/clusters/mbuf+clusters)

vmstat -i shows a rate of 1100 for the adapter.

The machine runs a fairly small PF configuration, but I've already
ruled it out, the symptoms appear when PF is disabled as well.

I'll happily provide more info.


Good, fast & cheap. Pick any two.

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