FreeBSD: syslog-ng: I/O error occurred while writing; fd='xx', error='No buffer space available (yy)'

Mark Blackman mark at
Fri Mar 23 09:15:47 UTC 2012

On 23 Mar 2012, at 08:58, Traiano Welcome wrote:

> Hi Mark
> On 22/03/2012 13:54, "Mark Blackman" <mark at> wrote:
>> On 22 Mar 2012, at 11:40, Traiano Welcome wrote:
>>> Somehow this doesn't strike  me as a large volume of throughput Š
>> Ok, fair enough. You might try simulating the problem by deliberately
>> overloading the syslog UDP output and confirm the cause.
> Apparently this means that the network driver has "filled" up with
> packets. John Baldwin over at freebsd-net@ advises I up the number of
> descriptors assigned to igb to the maximum
> to workaround this using the hw.igb.maxtxd tunable you would set. So I've
> rebooted with the following in loader.conf:
> hw.igb.rxd=4096
> hw.igb.txd=4096
> This seems to be working so far. What I've noticed is that the system is
> using far  less RAM than previously, and CPU utilisation is up to 100% of
> one core, load average is 1, which I would guess means that the system is
> now processing a lot more syslog  data now that "more packets are making
> it through the network driver".
> I'll keep monitoring over a 24 hour period though, to see how effective
> this is.

Right, good news. Interesting that you need to tweak network drivers.

- Mark

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