full socket buffers

[Mirek Lauš]

On Sat, Feb 5, 2011 at 8:07 PM, Glenn Satchell
<glenn.satchell at uniq.com.au> wrote:
> On 02/05/11 04:16, Mirek Lauš wrote:
>>
>> Hello again,
>>
>> On Sat, Dec 18, 2010 at 10:53 PM,<sthaug at nethelp.no>  wrote:
>>>>>
>>>>> We're also running 4.1.1p1, on FreeBSD 7.3-STABLE. Server hardware is
>>>>> Dell PE 1850, with two SCSI disks in a RAID-1 configuration. We have
>>>>> around 100k leases on two servers in a failover pair, with most of the
>>>>> pools on 24 hour leasetime. We don't see the problem you're seeing.
>>>>
>>>> We're running the dhcpd service on two IBM x3550 servers in failover,
>>>> both have two 74GB 15k disks in RAID-1 so very similar to yours.
>>>
>>> How many DISCOVERs and REQUESTs do you handle per second? Do you have
>>> battery backed cache for your RAID-1 config? Have you tried gstat, and
>>> looked at the %busy column?
>>>
>>> An additional point which might be relevant - we run our failover
>>> configuration with a "delayed-ack 28" setting. This cuts down on the
>>> failover traffic (including disk I/O). Yes, we know there have been
>>> some warnings about delayed-ack - however it has never given us any
>>> problems. Note that it needs to be explicitly compiled in.
>>
>> we have upgraded our RAID controller to ServeRAID 8k with 256MB write-back
>> cache. Few days later we have encountered the issue again. The kernel
>> starts
>> to drop UDP packets due to "full socket buffers". Only solution to
>> this situation
>> is a dhcpd process restart. I'm pointless. What would you recommend to
>> trace
>> down the cause of the issue?
>>
>> Regards,
>> Miroslav
>
> This is an operating system setting. Try google for your OS and something
> like "set udp buffer size".
>

This was of course the first thing we did before upgrading the RAID controller:

[root at dhcp1 ~]# sysctl kern.ipc.maxsockbuf
kern.ipc.maxsockbuf: 8388608

-ml