'dropped due to full socket buffers' by SNMP

[Victor Gamov]

Hi All

On 05.01.2021 12:39, Victor Gamov wrote:
> Hi Eugene!
> 
> Thanks for your responces.
> 
> And Happy New Year for everyone!
> 
> On 01.01.2021 03:19, Eugene Grosbein wrote:
>> 30.12.2020 23:08, Victor Gamov wrote:
>>
>>> As I understand hw.ix.flow_control=3 to allow flow-control for 
>>> negotiation.
>>> Real PAUSE setting will be set during negotiation.
>>
>> At the moment of congestion.
> 
> As I understand PAUSE feature negotiated during auto-negotiation 
> process. If flow-control disabled on one side (switch for example) then 
> other side (host) will not to use this feature too.  Is it right?
> 
>>>   So where I can find active flow-control setting for host interface?
>>
>> Can't check for ix just now, but for em(4) there is sysctl dev.em.0.fc.
>> It should be similar for ix.
> 
> I have hw.ix.flow_control=3 (what does is it means ?) and dev.ix.0.fc=3 
> (and what does is it means?)
> 
> 
>>>> maybe increase kern.ipc.maxsockbuf and then net.inet.udp.recvspace.
>>> Eugene, at first message you suppose Host-A (sender) "outgoing link 
>>> for that UDP packets is congested"
>>> because this host shows non-zero "dropped due to full socket buffers".
>>> So is net.inet.udp.recvspace increasing on Host-B (mainly receiver) 
>>> will be affected for this congestion?
>>
>> Can't tell in details without going deep into your setup :-)
>> You can try it yourself and verify quickly.
>>
>>> Or I need to try to increase both kern.ipc.maxsockbuf and 
>>> net.inet.udp.recvspace on both hosts?
>>
>> Tune one that drops UDP.
>>
>>> Also how I can check current sockbuf usage?
>>
>> netstat -xn
> 
> Unfortunately it never shoes counters about UDP multicast traffic.
> 
> I'll increase kern.ipc.maxsockbuf and net.inet.udp.recvspace at next 
> week and write about results.

I increase kern.ipc.maxsockbuf from 2097152 -> 2597152 -> 3145728 but
netstat -sn -p udp | grep 'dropped due to full socket buffers' still 
show dropped packets.

Then I increase net.inet.udp.recvspace 84160 -> 105200 but 'dropped due 
to full socket buffers' packets still here.

Do I need to try to increase something else?

-- 
CU,
Victor Gamov