4.2. Prioritizing Network Traffic

Procedure 4.2. Setting Network Priorities for File Sharing Services

1. The net_prio subsystem is not compiled in the kernel, it is a module that must be loaded manually. To do so, type:

   ~]# modprobe net_prio

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2. Attach the net_prio subsystem to the /cgroup/net_prio cgroup:

   ~]# mkdir /cgroup/net_prio
   ~]# mount -t cgroup -o net_prio net_prio /cgroup/net_prio

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3. Create two cgroups, one for each service:

   ~]# mkdir /cgroup/net_prio/nfs_high
   ~]# mkdir /cgroup/net_prio/samba_low

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4. To automatically move the nfs services to the nfs_high cgroup, add the following line to the /etc/sysconfig/nfs file:

   CGROUP_DAEMON="net_prio:nfs_high"

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   This configuration ensures that nfs service processes are moved to the nfs_high cgroup when the nfs service is started or restarted. For more information about moving service processes to cgroups, refer to Section 2.9.1, “Starting a Service in a Control Group”.
5. The smbd daemon does not have a configuration file in the /etc/sysconfig directory. To automatically move the smbd daemon to the samba_low cgroup, add the following line to the /etc/cgrules.conf file:

   *:smbd                net_prio                samba_low

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   Note that this rule moves every smbd daemon, not only /usr/sbin/smbd, into the samba_low cgroup.
   You can define rules for the nmbd and winbindd daemons to be moved to the samba_low cgroup in a similar way.
6. Start the cgred service to load the configuration from the previous step:

   ~]# service cgred start
   Starting CGroup Rules Engine Daemon:                       [  OK  ]
   

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7. For the purposes of this example, let us assume both services use the eth1 network interface. Define network priorities for each cgroup, where 1 denotes low priority and 10 denotes high priority:

   ~]# echo "eth1 1" > /cgroup/net_prio/samba_low
   ~]# echo "eth1 10" > /cgroup/net_prio/nfs_high

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8. Start the nfs and smb services and check whether their processes have been moved into the correct cgroups:

   ~]# service smb start
   Starting SMB services:                                     [  OK  ]
   ~]# cat /cgroup/net_prio/samba_low
   16122
   16124
   ~]# service nfs start
   Starting NFS services:                                     [  OK  ]
   Starting NFS quotas:                                       [  OK  ]
   Starting NFS mountd:                                       [  OK  ]
   Stopping RPC idmapd:                                       [  OK  ]
   Starting RPC idmapd:                                       [  OK  ]
   Starting NFS daemon:                                       [  OK  ]
   ~]# cat /cgroup/net_prio/nfs_high
   16321
   16325
   16376
   

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   Network traffic originating from NFS now has higher priority than traffic originating from Samba.