[f-nsp] BigIron MG8 hight CPU load on LP card

[sergp at soho.net.ua]

Hallo
We have the router :
HW: BigIron MG8 Router
SL M1: BIMG8-MR Management Module
Boot: Version 2.3.0jT105 Copyright © 1996-2003 Foundry Networks, Inc.
Monitor: Version 2.3.0jT105 Copyright © 1996-2003 Foundry Networks, Inc.
IronWare: Version 2.3.0jT103 Copyright © 1996-2003 Foundry Networks, Inc.

         Module Status Ports Starting MAC
M1 (upper): BIMG8-MR Management Module Active
M2 (lower): BIMG8-MR Management Module Standby (Ready State)
F1: BIMG8-SFM Switch Fabric Module Active
S1: BIMG8-1Gx40-SFP-v6 40 -port 1 GbE IPv4/v6 Module (IPv6 + OACL) 
CARD_STATE_UP 40
S5: BIMG8-10Gx8-v6 8 -port 10GbE IPv4/v6 Module (IPv6 + OACL) 
CARD_STATE_UP 8
S8: BIMG8-10Gx4-v6-A 4 -port 10GbE IPv4/v6 Module (IPv6 + OACL) 
CARD_STATE_UP 4

We have 5 BGP uplinks come through two 10Gb ports 5 and 8 modules. and 
five switches with servers connected 1Gb ports in 1 module .

When the total traffic of up to 1 gigabit but a relatively large number 
of small packets 400-600 Kpps cpu first module is loaded at 100% and 
start losing 80-90%.
while CPU on the control module and 10G modules in slots 5 and 8 are not 
loaded .

it looks like this:
show cpu lp
SLOT #: LP CPU UTILIZATION in%:
                in 1 second: in 5 seconds: in 60 seconds: in 300 seconds:
   1                 96                     96 100                    100
   5                  0                        0     1                   
      1
   8                  0                        0      0               
          0

show cpu
... Usage average for all tasks in the last 1 seconds ...
================================================== ========
Name         us /sec            %
idle         665002             100
...

if the number of packets reaches 1Mpps already traffic through 1 module 
does not go
and recovered only work when disconnected stream of small packets .

May be someone faced with a similar problem or have ideas what can i do?