numa_sched_launch.5 (2010 09)

n
numa_sched_launch(5) numa_sched_launch(5)
(Tunable Kernel Parameters)
NAME
numa_sched_launch - change process default launch policy
VALUES
Failsafe
0
Default
1
Allowed values
0: Disabled
1:Automatic
2: Enabled
Recommended values
1 unless the application requires explicit different behavior.
DESCRIPTION
The
numa_sched_launch
dynamic tunable controls the default launch policy for newly created
processes. The process launch policy controls the initial placement of the child process at creation time.
The scheduler can migrate threads from one locality domain (LDOM) to another to distribute workload
for better throughput and responsiveness. The default launch policy is applicable only to processes that
have no explicit launch policy, processor binding, or LDOM binding applied to them (see mpctl (2) for
details).
There are three possible values of this tunable:
numa_sched_launch = 0
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.
numa_sched_launch = 1
This is the default and recommended value. HP-UX will autosense the right policy setting
based on system 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 fork() to be placed in the same locality domain as the parent pro-
cess. 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
vfork() will be treated as if they are a new application and will con-
tinue to be launched using the legacy default launch policy.
numa_sched_launch = 2
This value explicitly enables the new default launch policy for processes. A process created
using fork() is placed in the same locality domain as its parent process irrespective of the
system configuration.
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 numa_sched_launch tunable changes take effect immediately. However, changes to this tunable
will not affect processes that are already created. Such processes will need to be stopped and restarted to
be launched with a modified tunable setting.
When Should the Value of This Tunable Be Changed to 0?
The value of
numa_sched_launch should be set to 0 to preserve the legacy process default launch pol-
icy even when the system is configured in LORA mode.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1