How to Optimize Linux for Packet Switching?

gabyz · 01-29-2014, 03:13 AM

I'm running 1Gb wirespeed 125B packets between 2 ports.

Code:

sudo brctl addbr br0
sudo brctl addif br0 eth1 eth2
sudo ip link set dev br0 up

Of the ~826,000 packets/sec I send to eth1 I get only ~216,000 pkts/sec out of eth2. If I activate tcpdump it drops to ~140,000 pkts/sec and I get
291300 packets captured
324048 packets received by filter
32748 packets dropped by kernel
1675952 packets dropped by interface
Most of the packets are dropped by the interface.

Using Ubuntu 13.04 with kernel 3.13 (latest)

Any ideas on how to reduce the packets dropped by the interface?

Thanks
Gaby

akiuni · 02-03-2014, 08:13 AM

Hi
You should try to identify which device is involved in that bridge. ifconfig gives you the counter "dropped:" for each device.
There may be many reasons why a packet is dropped, I suggest that you have a look inside your tcpdump result, especially, try to search "TCP retransmission requests" sent by your server. The root cause may be bad fragmentation (mtu), unsolicited or malformed data, crc error or networking errors like a bad link negociation etc... you can also have a look at your switch logs to find other clues.