[ILUG] extremely slow pop3, but imap is fine

[Justin Mason]

On Fri, Mar 27, 2009 at 10:03, Justin Mason <jm at jmason.org> wrote:
> On Fri, Mar 27, 2009 at 10:00, Kae Verens <kae at verens.com> wrote:
>> Kae Verens wrote:
>>>
>>> Kenn Humborg wrote:
>>>  >> On Thu, Mar 26, 2009 at 5:04 PM, Kae Verens <kae at verens.com> wrote:
>>>  >>> all was running perfectly for months until today.
>>>  >> Any patches applied? Anything showing on the logs? Tried to restart
>>>  >> services/box ?
>>>  >
>>>  > Run strace -p <PID> on the server process.  It might provide
>>>  > clues as to what's going on during the delays.
>>
>> turns out that another guy in our datacentre is having the same problem, so
>> this may be a router problem.
>>
>> any ideas why it would mostly affect POP3? appears to be slowing our other
>> services, but POP3 is the most serious.
>
> this looks to me like the kernel buffers are filling up, returning the
> EAGAIN ("try again later" basically) to the app level.  have you
> considered it may be a broken QoS policy or similar on the router
> deprioritising POP3 traffic?

hmm. also, when small packets get through fine but large packets
have trouble, that smells like MTU issues.