I have Linux that works as Router + traffic management with connection 
tracking enabled but without making NAT

About 600Mbit/s TX and 600Mbit/s RX forwarded traffic

iptables -L -n -v -t raw
Chain PREROUTING (policy ACCEPT 3340M packets, 2623G bytes)
 pkts bytes target     prot opt in     out     source               
destination
3339M 2621G NOTRACK    all  --  *      *       0.0.0.0/0            
0.0.0.0/0

Chain OUTPUT (policy ACCEPT 1978K packets, 157M bytes)
 pkts bytes target     prot opt in     out     source               
destination

iptables -L -n -v -t nat
Chain PREROUTING (policy ACCEPT 4073K packets, 299M bytes)
 pkts bytes target     prot opt in     out     source               
destination

Chain POSTROUTING (policy ACCEPT 3916K packets, 285M bytes)
 pkts bytes target     prot opt in     out     source               
destination

Chain OUTPUT (policy ACCEPT 604 packets, 29792 bytes)
 pkts bytes target     prot opt in     out     source               
destination


kernel 2.6.28.2
CPU: Core 2, speed 2999.98 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a 
unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        image name               app name                 
symbol name
14544205 15.8604  vmlinux                  vmlinux                  
ctnetlink_del_expect
11616986 12.6683  vmlinux                  vmlinux                  
native_read_tsc
6920732   7.5470  vmlinux                  vmlinux                  
_raw_spin_lock
3343941   3.6466  vmlinux                  vmlinux                  
mwait_idle
2176884   2.3739  vmlinux                  vmlinux                  
e1000_irq_enable
1513595   1.6506  vmlinux                  vmlinux                  
e1000_intr_msi
1319634   1.4391  vmlinux                  vmlinux                  
getnstimeofday
1265908   1.3805  vmlinux                  vmlinux                  
qdisc_graft
1178958   1.2857  vmlinux                  vmlinux        ...
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Pawe
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I will check this patch today at night.

--

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after patch i have:

CPU: Core 2, speed 3000 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a 
unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        image name               app name                 
symbol name
767616   13.0507  vmlinux                  vmlinux                  
u32_delete
291303    4.9526  vmlinux                  vmlinux                  
_raw_spin_trylock
269856    4.5880  vmlinux                  vmlinux                  
do_ipt_get_ctl
221887    3.7724  vmlinux                  vmlinux                  
devm_ioport_unmap
202405    3.4412  vmlinux                  vmlinux                  
devm_ioport_map
150375    2.5566  vmlinux                  vmlinux                  
native_calibrate_tsc
138476    2.3543  vmlinux                  vmlinux                  
update_persistent_clock
103328    1.7567  vmlinux                  vmlinux                  
update_wall_time
101648    1.7282  vmlinux                  vmlinux                  
e1000_xmit_frame
100776    1.7134  vmlinux                  vmlinux                  
__ip_route_output_key
94866     1.6129  vmlinux                  vmlinux                  
dev_ethtool
88844     1.5105  vmlinux                  vmlinux                  
dev_queue_xmit
88582     1.5060  vmlinux                  vmlinux                  
ixgbe_update_rx_dca
87747     1.4918  vmlinux                  vmlinux                  
__pskb_pull_tail
86888     1.4772  vmlinux                  vmlinux                  
irq_entries_start
77941     1.3251  vmlinux                  vmlinux                  
ixgbe_configure
76646     1.3031  vmlinux                  vmlinux                  
ixgbe_clean_rx_irq
75933     1.2910  vmlinux                  vmlinux                  
ixgbe_alloc_rx_buffers
75538     1.2843  vmlinux                  vmlinux                  
e1000_get_eeprom
75380     1.2816  vmlinux                  vmlinux                  ...
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