pset_create(2)pset_create(2)NAMEpset_create() - create a processor set
SYNOPSISDESCRIPTION
The function creates an empty processor set with no processors. Pro‐
cessor sets allow a subset of processors in the system to be isolated
for exclusive use by specified threads and processes. Only the threads
bound to a processor set can execute on processors in that processor
set. The binding of threads and processes to processor sets is con‐
trolled by the function (see pset_bind(2)).
A unique identifier is assigned to the new processor set created by the
function, and is returned to the caller in the memory location pointed
to by newpset. This value is valid only if the function return value
is zero.
A processor can be assigned to a processor set by the function. A pro‐
cessor may not belong to more than one processor set at a time. There
may be an implementation dependent limit on the maximum number of pro‐
cessor sets that may exist (created and not destroyed) at any given
time.
Any user may create a new processor set with the function. However,
special permissions are needed to populate a processor set with proces‐
sors (see pset_assign(2)), to execute applications in a processor set
(see pset_bind(2)), or to destroy a processor set (see
pset_destroy(2)). There may be a per user limit on how many processor
sets that users without the privilege may own.
Every processor set is assigned ownership and access permission
attributes. The creator of a processor set becomes the default owner
of the processor set.
The READ, WRITE, and EXEC access permissions are defined for processor
sets for three access modes — Owner, Group, and Others — similar to
the UNIX file system access permissions. The READ permission allows
the caller to query about processor set configuration, the WRITE per‐
mission allows the caller to change processor set configuration and
attributes, and the EXEC permission allows the caller to execute on
processors in the processor set. The function may be used to change
the ownership and access permissions, whereas the function may be used
to query the current ownership and access permissions.
A system default processor set is created at system initialization time
and cannot be destroyed. The default processor set is always owned by
the user with UID 0 and has the processor set ID of Processor 0 is
always assigned to the default processor set and cannot be reassigned
to another processor set.
Note on Hyper-Threading
On systems with the hyper-threading capability enabled at the firmware
level, each hyper-thread represents a logical processor (LCPU). Since
the logical processors in the same physical processor core share common
resources, interfaces dealing with workload migration or processor
migration must operate at the physical processor core granularity.
The following is a list of processor set attributes and their default
values at processor set creation time (see pset_getattr(2)):
Indicates the behavior on a request to bind a process
or a thread to a processor set that does not contain any pro‐
cessors. By default, such a request will be rejected.
GID of processor set's owner group.
The creator's gid is assigned by default.
A flag to indicate if processors in the set are
configured to receive external I/O interrupts or not. All
processors by default are made available to receive inter‐
rupts.
Indicates the behavior on a request to remove the last
processor from a processor set. By default, all pro‐
cesses/threads assigned to the processor set are reassigned
to the default processor set and the processor is reassigned
as requested.
On a system with the hyper-threading feature enabled, the LCPU
attribute
indicates whether or not the processor cores in a processor
set are enabled with logical processors (LCPU). By default,
the default processor set's attribute value is inherited at
the time of creation. The non-default processor set's can be
modified by but the default processor set's can only be modi‐
fied by the dynamic kernel tunable command,
Indicates the behavior on a request to destroy a
non-empty processor set. The non-empty processor set refers
to one that has at least one processor assigned to it. By
default, all processors and processes/threads assigned to the
processor set are reassigned to the system default processor
set, and the processor set is destroyed.
UID of the processor set owner.
The processor set creator is the default owner.
Access permissions for the processor set.
By default, the processor set owner has all permissions,
whereas group and others have only READ and EXEC permissions.
Processor sets define a scheduling allocation domain for threads and
processes. All threads may execute only on processors within the
assigned processor set. The kernel load balancers work within the pro‐
cessor set boundary. There is no load balancing across the processor
set boundary although users can explicitly migrate threads and pro‐
cesses from one processor set to another by using the function. The
POSIX RTSCHED scheduler (see rtsched(2)) no longer works at the system
level; its scheduling domain is restricted to the processor set bound‐
ary.
System daemon threads created in the kernel are not restricted to a
user defined processor set configuration. They may run on any proces‐
sor in the system as necessary.
Use with to see if the processor set functionality is supported by the
underlying HP-UX operating system version.
Security Restrictions
Some or all of the actions associated with this system call require the
privilege. Processes owned by the superuser have this privilege. Pro‐
cesses owned by other users may have this privilege, depending on sys‐
tem configuration. See privileges(5) for more information about privi‐
leged access on systems that support fine-grained privileges.
EXAMPLES
Create a new processor set:
RETURN VALUE
returns zero on successful completion. Otherwise, -1 is returned and
is set to indicate the error.
ERRORS
fails if one or more of the following is true:
The user has reached the per user limit on how many processor sets a
user without the privilege may own.
The memory location pointed to by
newpset is not writable by the user.
The memory location pointed to by
newpset is
Processor sets cannot be created on a uniprocessor system.
The user does not have necessary permissions to create a new processor
set.
A new processor set cannot be created at this time
due to lack of necessary system resources.
The processor set functionality is not supported by the
underlying HP-UX version.
SEE ALSOkctune(1M), psrset(1M), pset_assign(2), pset_bind(2), pset_ctl(2),
pset_destroy(2), pset_getattr(2), pset_setattr(2), rtsched(2),
sysconf(2), privgrp(4), privileges(5).
pset_create(2)
