'dropped due to full socket buffers' by SNMP

[Victor Gamov]

On 22.01.2021 16:09, Eugene Grosbein wrote:
> 22.01.2021 19:28, Victor Gamov wrote:
> 
>> On 22.01.2021 13:21, Eugene Grosbein wrote:
>>> 22.01.2021 17:02, Victor Gamov wrote:
>>>
>>>> No link overload: this host attached to network via 10G ix0, many
>>>> VLANs on this ix0 and some sender on every VLAN sends multicast
>>>> traffic to this host.  Total input traffic about 1Gbit/s
>>>
>>> What FreeBSD version do you use currently? Do you use IPv6 for UDP or
>>> IPv4 only?
>>
>>
>> FreeBSD 12.2-STABLE r366543 GENERIC  amd64
>>
>> UDP-4 only
> 
> In case of IPv4 UDP the counter "dropped due to full socket buffers"
> is increased for incoming packets only. Therefore, the problem is in a code
> processing incoming stream(s): either it locks for long time on something,
> or it just has no enough raw CPU horsepower to deal with incoming stream.
> 
> Look at "top -SHPI" CPU counters, if your CPU cores are loaded evenly;

it's CPU E3-1270 v6 @ 3.80GHz with WCPU about 60% idle + 9% 
kernel{if_io_tqg_X) + 5% intr{swi1: netisr X).  And many processes about 
1% WCPU for multicast receive/resend (one for every multicast)

Also "netstat -na -p udp" shows me zero or very small Recv-Q

> if some of cores became overloaded sometimes. You should also draw per-cpu load graphs.
> (f.e. sysctl kern.cp_times)

I have SNMP stats and it show me about 40% load


I have no visible problems with growing "dropped due to full socket 
buffers" but I think it's not well when this counter increasing.

-- 
CU,
Victor Gamov