dummynet dropping too many packets

[rihad]

Luigi Rizzo wrote:
> On Sun, Oct 04, 2009 at 06:47:23PM +0500, rihad wrote:
>> Hi, we have around 500-600 mbit/s traffic flowing through a 7.1R Dell 
>> PowerEdge w/ 2 GigE bce cards. There are currently around 4 thousand ISP 
>> users online limited by dummynet pipes of various speeds. According to 
>> netstat -s output around 500-1000 packets are being dropped every second 
>> (this accounts for wasting around 7-12 mbit/s worth of traffic according 
>> to systat -ifstat):
> 
> At those speeds you might be hitting various limits with your
> config (e.g. 50k nmbclusters is probably way too small for
> 4k users -- means you have an average of 10-15 buffers per user;
> the queue size of 350kbytes = 2.6Mbits means 2.6 seconds of buffering,
> which is quite high besides the fact that in order to scale to 4k users
> you would need over 1GB of kernel memory just for the buffers).


top output:
Mem: 2037M Active, 1248M Inact, 450M Wired, 184M Cache, 214M Buf, 17M Free

I guess we're quite far from reaching 1GB of kernel memory.