NAME
nfs3_max_threads — control the number of kernel threads that perform asynchronous I/O for the NFS version 3 client
VALUES
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 administrator.
DESCRIPTION
nfs3_max_threads
controls the number of kernel threads that perform asynchronous I/O for
the NFS version 3 client. Since NFS is based on RPC and RPC is inherently
synchronous, separate execution contexts are required to perform NFS
operations that are asynchronous from the calling thread. The operations
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
nfs3_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 2 and NFS version 3 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 network.
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 parameter 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://docs.hp.com.
AUTHOR
nfs3_max_threads
was developed by Sun Microsystems, Inc.
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