nfs4_max_threads.5 (2010 09)

n
nfs4_max_threads(5) nfs4_max_threads(5)
(Tunable Kernel Parameters)
NAME
nfs4_max_threads - control the number of kernel threads that perform asynchronous I/O for the NFS ver-
sion 4 client
VALUES
Failsafe
8
Default
8
Allowed values
Minimum: 0
Maximum: nkthread/5
Recommended values
A warning will be issued at runtime if the tunable is set to a value greater than 256 threads since this is
beyond the tested limit. This is not a serious warning but just an information message for the adminis-
trator.
DESCRIPTION
nfs4_max_threads controls the number of kernel threads that perform asynchronous I/O for the NFS
version 4 client. Since NFS is based on RPC and RPC is inherently synchronous, separate execution con-
texts are required to perform NFS operations that are asynchronous from the calling thread. The opera-
tions which can be executed asynchronously are read for read-ahead, readdir for readdir read-ahead, and
write for putpage and pageio requests.
Who Is Expected to Change This Tunable?
The distributed file system administrator should examine this value depending on the network bandwidth
available.
Restrictions on Changing
The
nfs4_max_threads
tunable is dynamic; however, the number of threads for a file system is set
when the file system is mounted. To affect a particular file system, unmount and mount the file system
after changing this parameter.
When Should the Value of This Tunable Be Raised?
If the network is very high bandwidth and the client and server have sufficient resources, increase this
value to more effectively utilize the available network bandwidth, the client resources, and the server
resources.
What Are the Side Effects of Raising the Value?
An increase in the system resources and the possibility that
nkthread (see nkthread (5)) may need to be
increased. The total number of asynchronous threads for NFS version 4 mount points cannot exceed 20%
of the available threads defined by nkthread. NFS mounts will fail if the NFS mount command cannot
guarantee the ability to create the maximum number of threads for that mount point.
When Should the Value of This Tunable Be Lowered?
In a very low bandwidth network, decrease this value so that the NFS client does not overload the net-
work.
What Are the Side Effects of Lowering the Value?
Decreasing this value may impact NFS performance.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its
meaning changed in future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-
ter values. After installation, some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable values, consult the documentation for
the kernel software being installed. For information about optional kernel software that was factory
installed on your system, see HP-UX Release Notes at
http://www.hp.com/go/hpux-core-docs.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1