Ring Buffer Configuration

I.4 Ring Buffer Configuration

To enable ring buffer configuration, use the KVM flavor and glance image. This increases the network throughout the VM.

Ensure that the ring buffer sizes are set to max on all the ethernet devices on the host machine.
1. Create /sbin/ifup-local file.
```
[root@DSR-Gen10-ol7 ova]# touch /sbin/ifup-local
```
2. Change the permission.
```
[root@DSR-Gen10-ol7 ova]# chmod +x /sbin/ifup-local
```
3. Change file security context.
```
[root@DSR-Gen10-ol7 ova]# chcon --reference /sbin/ifup /sbin/ifup-local
```
4. Before setting ring buffer value for VMs, verify the pre-set maximum value on the host machine of RX and TX for all the interfaces using the following command:
```
ethtool -g <interface-name> 
```
  For example:
```
/sbin/ethtool -g eth0 
/sbin/ethtool -g eth1 
/sbin/ethtool -g eth2 
/sbin/ethtool -g eth3 
```
  Sample output of above command:
```
ethtool -g eth0
Ring parameters for eth0:
Pre-set maximum:
RX:		4096
RX Mini:	n/a
RX Jumbo:	n/a
TX:		4096
Current hardware settings:
RX:		2080
RX Mini:	n/a
RX Jumbo:	n/a
TX:		2080
```
5. Use the pre-set maximum of RX and TX for each interface. Then, add the below script to file /sbin/ifup-local.
```
/sbin/ethtool -G <interface-name> rx <RX-Preset Maximum> tx <TX-Preset Maximum>
```
  For example:
```
#!/bin/bash
/sbin/ethtool -G eth0 rx 4078 tx 4096
/sbin/ethtool -G eth1 rx 4078 tx 4096
/sbin/ethtool -G eth2 rx 4078 tx 4096
/sbin/ethtool -G eth3 rx 4078 tx 4096
```
Verify that the ring buffer sizes are set to max on all the ethernet devices on the host machine:
```
# ethtool -g <ethernet adapter>
```
Verify the same for eth0, eth1, eth2 and eth3.
Restart all ethernet adapter eth0, eth1, eth2,eth3, one by one, by using the following command:
```
[root@DSR-Gen10-ol7 ova]# ifdown <ethernet adapter>
[root@DSR-Gen10-ol7 ova]# ifup <ethernet adapter> 
```
Verify again by using Step 2.