0% cpu usasge after fresh boot or net restart but 10% CPU if kernel flush route cache

cold cold
2010-01-26T16:58:32Z

HI,

i have expiriance some CPU usage spikes up to 10% on each four cpus
after the first kernel route cache flush.
After mashine start first 20 min CPU is 0%si  300Mbits/s full duplex
and arount 100k pps forwarded traffic, without any firewall, just
plain routing.

route -n |wc -l
34

ip route show cache | wc -l
2140842

cat /proc/sys/net/ipv4/route/secret_interval
600
cat /proc/sys/net/ipv4/route/max_size
33554432

after kernel  flush i got 10% on all CPUs for 5-6 mins.  It's not from
rebuilding route cashe becouse after
fresh boot or network restrat there is no CPU usage until kernel flush
route cache.
I try to play with rhash_entries= 300000 to 2000000 same result.

Network Card: Ethernet controller: Intel Corporation 82576 Gigabit
Network Connection
CPU: Intel(R) Xeon(R) CPU           E5420  @ 2.50GHz
RAM: 4G
Kernel: vanilla 2.6.32.4