dummynet dropping too many packets

rihad rihad at mail.ru
Mon Oct 5 17:23:57 UTC 2009

Julian Elischer wrote:
> Luigi Rizzo wrote:
>>> Taildrop does not really help with this. GRED does much better.
>> i think the first problem here is figure out _why_ we have
>> the drops, as the original poster said that queues are configured
>> with a very large amount of buffer (and i think there is a
>> misconfiguration somewhere because the mbuf stats do not make
>> sense)
> it all depends on the characteristics of the traffic
> you need different queue lengths if it is just a small number of high 
> speeed sessions (and mayne a large number of slow speed sessions),
> or if it is a larger number of medium speed sessions.
> Is it possible to know what sessions are losing packets?
Yes, of course, by running ipfw pipe show ;-)
There's one confusing thing, though: net.inet.ip.dummynet.io_pkt_drop 
isn't increasing while around 800-1000 packets per second are being 
dropped right now. And so "ipfw pipe show" Drp column wouldn't grow 
either. So it's either not dummynet dropping packets, or a bug (?).

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