dummynet high cpu load

[Miroslav Slavkov]

Hello,

 I have a strange thing going on with dummynet. I'm loading around 11000 pipes.
 The machine does not forward, generate or receive any traffic. The only running service is ssh. It's for developing purposes.

 The thing happening is when loading more than 10700 pipes. The dummynet process begins to eat around %50 of cpu. If i load only 10000 pipes, it is using 0% cpu.
 
 Some output:

# ipfw show
65535 612000 126865054 allow ip from any to any

# ipfw pipe show| wc -l
    10001

# top -Sd 2
last pid: 35787;  load averages:  0.11,  0.17,  0.16                                                                           up 0+11:29:29  01:53:51
73 processes:  6 running, 53 sleeping, 14 waiting
CPU:  0.0% user,  0.0% nice, 25.1% system,  0.2% interrupt, 74.7% idle
Mem: 23M Active, 20M Inact, 156M Wired, 48K Cache, 38M Buf, 781M Free
Swap: 4096M Total, 4096M Free

  PID USERNAME       THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
   12 root             1 171 ki31     0K    16K RUN    0 566:04 99.37% idle: cpu0
   11 root             1 171 ki31     0K    16K RUN    1 459:35 99.07% idle: cpu1
   36 root             1 -68    -     0K    16K CPU0   0 343:55  0.00% dummynet


Still.. while loading the rules (one row per pipe config, with script for pipe counting...) the dummynet process begins to raise the usage after 4000 or some pipes. It gets to 0% after 10-20 secs.


# ipfw pipe show | wc -l
   10701

# top -Sd2
last pid: 57219;  load averages:  0.32,  0.23,  0.18                                                                           up 0+11:37:13  02:01:35
73 processes:  5 running, 54 sleeping, 14 waiting
CPU:  0.0% user,  0.0% nice, 25.2% system,  0.0% interrupt, 74.8% idle
Mem: 23M Active, 21M Inact, 156M Wired, 48K Cache, 38M Buf, 781M Free
Swap: 4096M Total, 4096M Free

  PID USERNAME       THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
   11 root             1 171 ki31     0K    16K RUN    1 465:48 91.26% idle: cpu1
   12 root             1 171 ki31     0K    16K RUN    0 568:09 59.38% idle: cpu0
   36 root             1 -68    -     0K    16K CPU0   0 350:22 51.56% dummynet


# uname -rp
7.1-STABLE amd64

The system is last updated on 15 Jan 2009.

The pipes are simple enough: ipfw pipe X config bw ????Kbit/s
Seems strange, because no rules are applied. The load is still around 50% even if the firewall is turned off with the sysctl option.

Any clues?