pthread_launch_policy_np(3T)pthread_launch_policy_np(3T)NAMEpthread_launch_policy_np() - setting thread launch policies
SYNOPSISPARAMETERS
request This parameter determines the precise action to be
taken by these functions.
answer This parameter is an output parameter in which values
are returned. The meaning of answer depends on request
parameter.
tid This parameter gives the value of the thread id for
certain requests.
DESCRIPTION
Each process shall have a launch policy. Each thread shall have a
launch policy. The launch policy for a thread does not have to match
the launch policy for the process. The launch policy determines the
locality domain where the newly created process or thread will be
launched in a ccNUMA system. The locality domains covered by a
process's or thread's processor set are the available locality domains.
The function sets a thread launch policy for a specific thread. The
thread specified by tid is the target thread whose launch policy is
changed. The value can be used to refer to the calling thread.
is currently not supported for threads. If is used on a thread, it is
silently ignored and zero is returned for successful completion.
When a process creates another process (via or the child process will
inherit the parent process's launch policy. The initial thread in the
child process will inherit the launch policy of the creating thread
(and not that of its process). Other threads in a multi-threaded
process inherit their launch policy from the creating thread.
For all launch policies, the target thread is bound to the locality
domain on which it was launched. The target is allowed to execute on
any processor within that locality domain.
When setting a launch policy, if the target already has processor or
locality domain binding, the existing binding will not be overwritten.
Instead the locality domain in which the target is bound (whether
locality domain binding or processor binding) will be used as the
starting locality domain for implementing the launch policy.
Refer to mpctl(2) man page for further details on launch policies.
Note: locality domains are tightly tied to the physical components of
the underlying system. As a result, the performance observed when
using launch policies based on locality domains may vary from system to
system. For example, a system which contains 4 locality domains, each
containing 32 processors, may exhibit different performance behaviors
from a system that contains 32 locality domains with 4 processors per
domain. The launch policy that provides optimal performance on one sys‐
tem may not provide optimal performance on a different system for the
same application.
The request parameter specifies the action to take and may be one of
the following:
The current launch policy of the target thread is returned in
the
answer parameter. This request currently returns or to
indicate the current launch policy of the thread speci‐
fied by tid. Other launch policies may be added in
future releases and returned via this option. Applica‐
tions using this option should be written to handle other
return values in order to continue working on future
releases.
This request establishes a round robin launch policy
for the specified thread. The successive child threads
of the specified thread will be launched on different
locality domains in a round robin manner until all avail‐
able locality domains have been used by threads in the
launch tree. At that point, the selection of locality
domains begins again from the original locality domain.
The answer parameter is ignored.
This request establishes a fill first launch policy
for the specified thread. The successive child threads
of the specified thread will be launched on the same
locality domain as their parent thread until one thread
has been created for each available processor in the
domain. At that point, a new locality domain is selected
and successive threads are launched there until there is
one thread per processor. All available locality domains
will be used before the original domain is selected
again. The answer parameter is ignored.
This request establishes a packed launch policy
for the specified thread. The successive child threads
are launched on the same locality domain as their parent
thread. The answer parameter is ignored.
This request establishes a least loaded launch policy
for the specified thread. The successive child threads
are launched on the least loaded locality domain in the
processor set regardless of the location of their parent
thread. The answer parameter is ignored.
This request establishes a tree based round robin launch policy
for the specified thread. This request differs from in
which threads become part of the launch tree. This
launch policy includes all descendents of the target
thread in the launch tree. The answer parameter is
ignored.
This request establishes a tree based fill first launch policy
for the specified thread. This request differs from in
which threads become part of the launch tree. This
launch policy includes all descendents of the target
thread in the launch tree. The answer parameter is
ignored.
This request unsets any launch policy in the thread. The system
will employ
a default, optimal policy in determining where the newly
created thread will be launched. The existing binding of
the thread is not changed. The answer parameter is
ignored.
RETURN VALUE
Upon successful completion, returns zero. Otherwise, an error number
is returned to indicate the error (the variable is not set).
ERRORS
If any of the following occur, the function returns the corresponding
error number:
[EINVAL] The request parameter contains an illegal value.
[EINVAL] The value specified by answer is illegal.
[ESRCH] No thread could be found in the current process
that matches the thread ID specified in tid.
WARNINGS
is currently not supported for threads. If is used on a thread, it is
silently ignored and zero is returned for successful completion. If the
request parameter is answer is set to For all other request values,
answer parameter is ignored. Applications dependent on the complete
implementation of should use threads.
AUTHOR
was developed by HP.
SEE ALSOmpctl(2), sleep(3C), rtsched(2).
STANDARDS CONFORMANCE
Pthread Library pthread_launch_policy_np(3T)
