NUMA_cpu_level_mask \- return mask of CPUs at given distance

.nf

.B #include <libNUMA.h>

.BI "ssize_t NUMA_cpu_level_mask (size_t " destsize ", cpu_set_t *" dest ","

.BI " size_t " srcsize ", const cpu_set_t *" src ","

.BI " unsigned int " level );

.fi

.BR NUMA_cpu_level_mask ()

sets the bits corresponding to all CPU the are at or below distance

.IR level

from the CPUs with bits set in

.IR src

and set the bits for all the CPUs in

.IR dest .

Level 1 corresponds to all thread siblings of the input CPUs. Level 2

corresponds to all core siblings. Higher levels are measured by the access

cost of the memory. For non-NUMA machines there is only one additional

level. For NUMA machines there can be many different levels, depending

on the number of memory controllers in the system and the access times.

On success

.BR NUMA_cpu_level_mask ()

returns a nonnegative number.

On error, \-1 is returned and

.I errno

is set to indicate the error.

This interface is Linux-specific.

The information for levels 3 and higher depends on measures of access times

for the different sockets. This information is often provided by the kernel

and it is plainly very often wrong. Access times which differ in practice

are shown as equal. The

.BR NUMA_cpu_level_mask ()

interface tries its best to provide the correct information.

.BR CPU_COUNT_S (3)

.BR NUMA_cpu_system_mask (3)

.BR NUMA_cpu_self_mask (3)