Managing NFS and KRPC Kernel Configurations in HP-UX 11i v2 (November 2013)

This tunable is not available in the next release of HP-UX. Starting with the HP-UX 11i v3 release,

conformity with POSIX standards is the default behavior and is not user-configurable.

2.1.10 nfs_wakeup_one

Description

The nfs_wakeup_one tunable enables you to specify whether the NFS client activates all NFS threads

or only a single NFS thread waiting for the same rnode lock. It also enables you to specify whether

the NFS client activates all sleeping biods or only a single sleeping biod while servicing a new read

or write request. Waking all the NFS threads can result in increased CPU utilization on the client

system. In many cases, enabling the nfs_wakeup_one tunable can reduce overall CPU utilization on

the client and help improve application performance.

CPU utilization increases over time if multiple threads and processes lookup, create, and delete

numerous files in the same directory over NFS. This increase is because of the rnode locks in NFS that

use the sleep/wakeup mechanism. CPU utilization also increases when all biods are activated

because of asynchronous read and write requests. This tunable replaces the sleep/wakeup

mechanism with the sleep_one/wakeup_one mechanism.

Tested values

Default: 0 (Tunable is disabled)

Min: 0

Max: 2 (Tunable is enabled)

Note: The nfs_wakeup_one tunable was first introduced with

patch PHNE_33982 and accepted only two values: 0 and

1. Beginning with patch PHNE_35118, the

nfs_wakeup_one tunable is modified to accept three values:

0, 1, and 2.

Restrictions on changing

The nfs_wakeup_one tunable is dynamic. System reboot is not required to activate a change made to

this tunable. Changes made to the nfs_wakeup_one tunable are applicable to all NFS mounted

filesystems.

Note: If there are no NFS mount points in the system, any

change made to the value of the tunable is effective

immediately. If there are NFS mount points in the system, a

system reboot is required for the change to be activated.

Modifying the value

When the nfs_wakeup_one tunable is set to 1, CPU utilization is reduced for NFS applications for

create, lookup or delete files. When set to 2, the performance benefits for create, lookup, and delete

are maintained and CPU utilization is also reduced when applications read from NFS files and write

to NFS files.

This tunable is not available in the next release of HP-UX. Starting with the HP-UX 11i v3 release, this

behavior is enabled by default and is not user-configurable.