Tip of the Day: Tuning the Kernel NFS Client for RHEL4 through RHEL6.3 and Delphix

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  • Updated 5 years ago
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Tuning the Kernel NFS Client In Linux, the number of simultaneous NFS requests is limited by the Remote Procedure Call (RPC) subsystem. The maximum number of simultaneous requests defaults to 16. Maximize the number of simultaneous requests by changing the kernel tunable sunrpc.tcp_slot_table_entries value to 128.  

  1. As superuser, run the following command to change the instantaneous value of simultaneous RPC commands:

    # sysctl -w sunrpc.tcp_slot_table_entries=128
  2. Edit the file /etc/modprobe.d/modprobe.conf.dist and change the line:

    install sunrpc /sbin/modprobe --first-time --ignore-install sunrpc && { /bin/mount -t rpc_pipefs sunrpc /var/lib/nfs/rpc_pipefs > /dev/null 2>&1 || :;                                                                                                                                                                                                                                        to

    install sunrpc /sbin/modprobe --first-time --ignore-install sunrpc && { /bin/mount -t rpc_pipefs sunrpc /var/lib/nfs/rpc_pipefs > /dev/null 2>&1 ; /sbin/sysctl -w sunrpc.tcp_slot_table_entries=128; } *Improper changes to the modprobe.conf.dist file may disrupt use of NFS on the system. Check with your system administrator or operating system vendor for assistance. Save a copy of the modprobe.conf.dist in a directory other than /etc/modprobe.d before starting.

RHEL 5.7 through RHEL 6.2
  1. As superuser, run the following command to change the instantaneous value of simultaneous RPC commands:

    # sysctl -w sunrpc.tcp_slot_table_entries=128
  2. If it doesn't already exist, create the file /etc/modprobe.d/rpcinfo with the following contents:

    options sunrpc tcp_slot_table_entries=128
RHEL 6.3 onwards Beginning with RHEL 6.3, the number of RPC slots is dynamically managed by the system and does not need to be tuned. Although the sunrpc.tcp_slot_table_entries tuneable still exists, it has a default value of 2, instead of 16 as in prior releases. The maximum number of simultaneous requests is determined by the new tuneable,  sunrpc.tcp_max_slot_table_entries, which has a default value of 65535.

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Posted 5 years ago

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