dummynet dropping too many packets

[rihad]

rihad wrote:
> Julian Elischer wrote:
>> rihad wrote:
>>> Luigi Rizzo wrote:
>>>> 2. your test with 'ipfw allow ip from any to any' does not
>>>>    prove that the interface queue is not saturating, because
>>>>    you also remove the burstiness that dummynet introduces,
>>>>    and so the queue is driven differently.
>>>>
>>>
>>> How do I investigate and fix this burstiness issue?
>>
>> higher Hz rate?
>>
> 
> Rebooted with HZ=2000 10 minutes ago. Due to application design the ipfw 
>  table (pipe tablearg) was flushed, so there are now 350 (and increasing 
> at a rate 1 per 1-2 seconds as I type this) or so users in the table, 
> and not 4k as normally would be. The box is servicing 450+ mbit/s 
> without a single drop. I want to monitor how things change once the 
> number of users in ipfw tables gradually increases up to several thousands.
> 

It starts dropping packets at around 2000 online users (ipfw table 
load). I've set up a shell script to monitor this:

# while :; do ipfw table 0 list | wc -l; netstat -s 2>/dev/null |fgrep 
-w 'output packets dropped'; sleep 10; done

... # all zeroes above this
     1999
         0 output packets dropped due to no bufs, etc.
     2001
         0 output packets dropped due to no bufs, etc.
     2008
         0 output packets dropped due to no bufs, etc.
     2017
         0 output packets dropped due to no bufs, etc.
     2027
         156 output packets dropped due to no bufs, etc.
     2037
         156 output packets dropped due to no bufs, etc.
     2045
         156 output packets dropped due to no bufs, etc.
     2372
         202 output packets dropped due to no bufs, etc.
     2377
         207 output packets dropped due to no bufs, etc.
     2391
         338 output packets dropped due to no bufs, etc.
     2402
         394 output packets dropped due to no bufs, etc.
     2415
         531 output packets dropped due to no bufs, etc.
     2421
         725 output packets dropped due to no bufs, etc.


Is there some limit on the number of IP addresses in an ipfw table?