mpctl.2 (2010 09)

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mpctl(2) mpctl(2)

MPC_LDOMCORES Returns the number of enabled processor cores assigned to the current processor

set in the locality domain; this value will always be greater than or equal to 0.

The pid argument is ignored.

Processor and Locality Domain Binding

Each process shall have a processor and locality domain binding. Each LWP (lightweight process) shall

have a processor and locality domain binding. The binding assignments for a lightweight process do not

have to match the binding assignments for the process.

Setting the processor or locality domain binding on the process of a multithreaded process, causes all

LWPs (lightweight processes) in the target process to have their binding assignments changed to what is

speciﬁed. However, if any LWP belongs to a different processor set such that the speciﬁed processor or

locality domain does not contribute to that processor set, the binding assignment for such an LWP is not

changed.

When a process creates another process (via

fork()

or vfork()), the child process will inherit the

parent process’s binding assignments (NOT the binding assignments of the creating LWP). The initial

LWP in the child process shall inherit its binding assignments from the child process. LWPs other than

the initial LWP shall inherit their binding assignments from the creating LWP (unless speciﬁed otherwise

in the LWP create attributes).

Processor binding and locality domain binding are mutually exclusive -- only one can be in effect at any

time. If locality domain binding is in effect, the target is allowed to execute on any processor within that

locality domain in its processor set.

Setting the processor or locality domain binding will fail if the target processor or locality domain is not in

the processor set of the speciﬁed process or LWP.

WARNING: Due to the capability of online addition and deletion of processors on some platforms, proces-

sors may go away. If this occurs, any processes or LWPs bound to a departing processor will be rebound

to a different processor with the same binding type. If the last processor in a locality domain is removed,

any processes or LWPs bound to a departing locality domain will be rebound to a different locality

domain.

For processor binding use:

int mpctl(mpc_request_t request, spu_t spu, pid_t pid);

int mpctl(mpc_request_t request, spu_t spu, lwpid_t lwpid);

The request argument determines the precise action to be taken by mpctl() and is one of the following:

MPC_SETPROCESS

This call is advisory . This request asynchronously assigns process pid to proces-

sor spu . The new processor assignment is returned.

The pid

MPC_SELFPID may be used to refer to the calling process.

The spu

MPC_SPUNOCHANGE may be passed to read the current assignment.

The spu MPC_SPUFLOAT may be used to break any speciﬁc-processor assign-

ment. This allows the process to ﬂoat to any processor.

NOTE: This call is advisory . If the scheduling policy for a process conﬂicts with

this processor assignment, the scheduling policy takes precedence. For example,

when a processor is ready to choose another process to execute, and the highest

priority

SCHED_FIFO process is bound to a different processor, that process will

execute on the selecting processor rather than waiting for the speciﬁed processor

to which it was bound.

If the process speciﬁed by pid is a multithreaded process, all LWPs (lightweight

processes) in the target process with the same processor set binding as the target

process will have their processor assignment changed to what is speciﬁed. The

processor set binding takes precedence over processor or locality domain bind-

ing.

MPC_SETPROCESS_FORCE

This call is identical to MPC_SETPROCESS except that the processor binding

will take precedence over the scheduling policy. This call is synchronous. For

example, when a processor is ready to choose another process to execute, and the

highest priority SCHED_FIFO process is bound to a different processor, that

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