numa_sched_launch(5)numa_sched_launch(5)NAMEnuma_sched_launch - change process default launch policy
VALUES
Failsafe
Default
Allowed values
Recommended values
unless the application requires explicit different behavior.
DESCRIPTION
The dynamic tunable controls the default launch policy for newly cre‐
ated processes. The process launch policy controls the initial place‐
ment of the child process at creation time. The scheduler can migrate
threads from one locality domain (LDOM) to another to distribute work‐
load for better throughput and responsiveness. The default launch pol‐
icy is applicable only to processes that have no explicit launch pol‐
icy, processor binding, or LDOM binding applied to them (see mpctl(2)
for details).
There are four possible values of this tunable:
This value explicitly disables any change in the default launch
policy for
processes irrespective of the system configuration. A
newly created process will be placed using the legacy
default launch policy.
This is the default and recommended value.
HP-UX will autosense the right policy setting based on sys‐
tem configuration. This policy directs HP-UX to optimize
the launch policy for multi-process applications that share
data. Such applications can get better performance when
the applications are packed together in the same LDOM. The
policy will cause child processes created using to be
placed in the same locality domain as the parent process.
Note that a different default launch policy may be used in
the future with new system configurations for improved
application performance when this tunable is enabled.
Processes created using will be treated as if they are a
new application and will continue to be launched using the
legacy default launch policy.
This value explicitly enables the new default launch policy for
processes.
A process created using is placed in the same locality
domain as its parent process irrespective of the system
configuration.
This value explicitly enables the new default launch policy for
processes.
When selecting the locality domain, the scheduler attempts
to pack the threads in the same locality if the current
load is below a certain threshold.
Who Is Expected to Change This Tunable?
System administrators who prefer to explicitly control the default
launch policy for applications even when LORA (Locality Optimized
Resource Alignment) mode is enabled (see numa_policy(5) for details).
Restrictions on Changing
The tunable changes take effect immediately. However, changes to this
tunable will not affect processes that are already created. Such pro‐
cesses will need to be stopped and restarted to be launched with a mod‐
ified tunable setting.
When Should the Value of This Tunable Be Changed to 0?
The value of should be set to to preserve the legacy process default
launch policy even when the system is configured in LORA mode.
When Should the Value of This Tunable Be Changed to 1?
The value of should be set to to improve the performance of multi-
process applications.
When Should the Value of This Tunable Be Changed to 2?
The value of should be set to when a multi-process application is
likely to see improved performance even if the system is not configured
for LORA mode.
When Should the Value of This Tunable Be Changed to 3?
The value of should be set to when a multi-threaded application is
likely to see improved performance by keeping the threads densely
packed in the LDOMs, even if the system is not configured for LORA
mode.
What Are the Side Effects of Changing the Value?
The distribution of CPU utilization across the system will change.
This situation can result in a change in performance. The change in
performance is highly dependent on the workload and the partition con‐
figuration.
What Other Tunable Values Should Be Changed at the Same Time?
None.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parame‐
ter 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 val‐
ues. For information about the effects of installation on tunable val‐
ues, consult the documentation for the kernel software being installed.
For information about optional kernel software that was factory
installed on your system, see at
AUTHOR
was developed by HP.
SEE ALSOfork(2), mpctl(2), vfork(2), numa_policy(5).
Tunable Kernel Parameters numa_sched_launch(5)
