bind_to_cpu(3)bind_to_cpu(3)NAME
bind_to_cpu, bind_to_cpu_id - Bind execution to a specific CPU
SYNOPSIS
#include <sys/types.h> #include <sys/resource.h> #include <sys/proces‐
sor.h>
int bind_to_cpu(
pid_t pid,
unsigned long cpu_mask,
unsigned long flag ); int bind_to_cpu_id(
pid_t pid,
long cpu_id,
unsigned long flag );
LIBRARY
Mach Library (libmach.a)
PARAMETERS
Specifies the target pid. You must have access rights to the pid.
Specifies the CPU on which the thread should run. The target CPU is the
bit index in the mask. If you set more than one bit, an error is gener‐
ated. A cpu_mask of zero clears any previously set CPU binding. Speci‐
fies flags for the CPU binding. Currently, only the BIND_NO_INHERIT
flag is supported. When set, this flag causes child processes and
threads to not inherit the CPU binding. Specifies the CPU on which the
thread should run. The target CPU is the number of the CPU.
DESCRIPTION
Upon return from bind_to_cpu() or bind_to_cpu_id(), all threads of the
target pid are running on the target CPU. Bound threads are not eligi‐
ble for execution on any other CPU. You release CPU binding by invoking
bind_to_cpu() with a cpu_mask of zero.
RETURN VALUES
Upon successful completion, bind_to_cpu() and bind_to_cpu_id() both
return zero. Upon error, a -1 is returned and errno is set to indicate
the error.
ERRORS
The operation did not have proper access permissions. The call passed
an invalid argument. The specified process or child process ID is
invalid or not in use.
EXAMPLES
/*
* Fork child process and force it to run on cpu number 3.
* Processes created by the forked child will not inherit bindings.
*/ #include <sys/resource.h> #include <sys/sysinfo.h> #include
<sys/signal.h> #include <sys/types.h> #include <sys/processor.h>
#define CPU_3 0x8 /* Bit 3 set */
main() {
pid_t pid;
if (pid = fork()) { /* parent */
if (bind_to_cpu(pid, CPU_3, BIND_NO_INHERIT)) {
kill(pid, SIGKILL);
exit(1); /* bind_to_cpu will print error msg */
}
sleep(2); /* wait for child to print CPU */
}
else { /* child */
long cpu_num;
sleep(1); /* wait for parent to bind CPU */
getsysinfo(GSI_CURRENT_CPU, &cpu_num, sizeof(cpu_num), 0L, 0L,
0L);
printf("child running on CPU %d\n", cpu_num);
} }
In this example, the CPU_3 symbol is defined so that bit three in the
bit mask is set. When the pid returned from the fork() routine identi‐
fies the parent routine, the bind_to_cpu() routine is called. This rou‐
tine binds the child process to CPU number three, as specified in the
CPU_3 symbol. When the pid returned from the fork() routine identifies
the child routine, the child routine sleeps to give the parent routine
time to set its CPU binding. Then it uses the getsysinfo() call to
determine its CPU and displays its CPU with the printf() routine.
If the return value from the bind_to_cpu() or bind_to_cpu_id() routine
indicates an error, the parent process kills the child process and
exits with an error status.
SEE ALSO
Commands: runon(1)
Functions: getsysinfo(2)bind_to_cpu(3)