pset_create(2) pset_create(2)
NAME [Toc] [Back]
pset_create - create a processor set
SYNOPSIS [Toc] [Back]
#include <sys/pset.h>
int pset_create(
psetid_t *newpset);
DESCRIPTION [Toc] [Back]
The pset_create() function creates an empty processor set with no
processors. Processor 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 controlled by the pset_bind() function (see pset_bind(2)).
A unique identifier is assigned to the new processor set created by
the pset_create() 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 pset_assign()
function. A processor may not belong to more than one processor set at
a time. There may be an implementation dependent limit on the maximum
number of processor sets that may exist (created and not destroyed) at
any given time.
Any user may create a new processor set with the pset_create()
function. However, special permissions are needed to populate a
processor set with processors (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 non-privileged users 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
permission 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 pset_setattr() function may be
used to change the ownership and access permissions, whereas the
pset_getattr() function may be used to query the current ownership and
access permissions.
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pset_create(2) pset_create(2)
A system default processor set is created at system initialization
time and cannot be destroyed. The default processor set is always
owned by the superuser and has the processor set ID of PS_DEFAULT.
Processor 0 is always assigned to the default processor set and cannot
be reassigned to another processor set.
The following is a list of processor set attributes and their default
values at processor set creation time (see pset_getattr(2) for
details):
PSET_ATTR_EMPTY [Toc] [Back]
Indicates the behavior on a request to bind a process or a
thread to a processor set that does not contain any
processors. By default, such a request will be rejected.
PSET_ATTR_GRPID [Toc] [Back]
GID of processor set's owner group. The creator's gid is
assigned by default.
PSET_ATTR_IOINTR [Toc] [Back]
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 interrupts.
PSET_ATTR_LASTSPU [Toc] [Back]
Indicates the behavior on a request to remove the last
processor from a processor set. By default, all
processes/threads assigned to the processor set are
reassigned to the default processor set and the processor is
reassigned as requested.
PSET_ATTR_NONEMPTY [Toc] [Back]
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.
PSET_ATTR_OWNID [Toc] [Back]
UID of the processor set owner. The processor set creator is
the default owner.
PSET_ATTR_PERM [Toc] [Back]
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
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pset_create(2) pset_create(2)
processor set boundary. There is no load balancing across the
processor set boundary although users can explicitly migrate threads
and processes from one processor set to another by using the
pset_bind() function. The POSIX RTSCHED scheduler (see rtsched(2)) no
longer works at the system level; its scheduling domain is restricted
to the processor set boundary.
System daemon threads created in the kernel are not restricted to a
user defined processor set configuration. They may run on any
processor in the system as necessary.
Use sysconf() with _SC_PSET_SUPPORT to see if the processor set
functionality is supported by the underlying HP-UX operating system
version.
EXAMPLE [Toc] [Back]
Create a new processor set:
#include <sys/pset.h>
psetid_t new_psetid;
int ret;
if ((ret = pset_create(&new_psetid)) < 0) {
perror("pset_create()");
exit(1);
}
RETURN VALUE [Toc] [Back]
pset_create returns zero on successful completion. Otherwise, -1 is
returned and errno is set to indicate the error.
ERRORS [Toc] [Back]
pset_create fails if one or more of the following is true:
[EAGAIN] The user has reached the per user limit on how many
processor sets a non-privileged user may own.
[EFAULT] The memory location pointed to by newpset is not writable
by the user.
[EINVAL] The memory location pointed to by newpset is NULL.
[EINVAL] Processor sets cannot be created on a uniprocessor system.
[EPERM] The user does not have necessary permissions to create a
new processor set.
[ENOMEM] A new processor set cannot be created due to lack of
necessary system resources at this time.
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pset_create(2) pset_create(2)
[ENOSYS] The processor set functionality is not supported by the
underlying HP-UX version.
SEE ALSO [Toc] [Back]
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).
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