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/* This example program plays with:
* - retrieving and changing CPU binding of current process and thread
* - retrieving the location where the current thread executes
* - combining/modifying cpusets using the bitmap API
*
* Copyright © 2014-2018 Inria. All rights reserved.
* See COPYING in top-level directory.
*/
#include "hwloc.h"
#include <errno.h>
#include <stdio.h>
#include <string.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
int main(void)
{
hwloc_topology_t topology;
hwloc_bitmap_t set, set2;
hwloc_const_bitmap_t cset_available, cset_all;
hwloc_obj_t obj;
char *buffer;
char type[64];
unsigned i;
int err;
/* create a topology */
err = hwloc_topology_init(&topology);
if (err < 0) {
fprintf(stderr, "failed to initialize the topology\n");
return EXIT_FAILURE;
}
err = hwloc_topology_load(topology);
if (err < 0) {
fprintf(stderr, "failed to load the topology\n");
hwloc_topology_destroy(topology);
return EXIT_FAILURE;
}
/* retrieve the entire set of available PUs */
cset_available = hwloc_topology_get_topology_cpuset(topology);
/* retrieve the CPU binding of the current entire process */
set = hwloc_bitmap_alloc();
if (!set) {
fprintf(stderr, "failed to allocate a bitmap\n");
hwloc_topology_destroy(topology);
return EXIT_FAILURE;
}
err = hwloc_get_cpubind(topology, set, HWLOC_CPUBIND_PROCESS);
if (err < 0) {
fprintf(stderr, "failed to get cpu binding\n");
hwloc_bitmap_free(set);
hwloc_topology_destroy(topology);
return EXIT_FAILURE;
}
/* display the processing units that cannot be used by this process */
if (hwloc_bitmap_isequal(set, cset_available)) {
printf("this process can use all available processing units in the system\n");
} else {
/* compute the set where we currently cannot run.
* we can't modify cset_available because it's a system read-only one,
* so we do set = available &~ set
*/
hwloc_bitmap_andnot(set, cset_available, set);
hwloc_bitmap_asprintf(&buffer, set);
printf("process cannot use %d process units (%s) among %d in the system\n",
hwloc_bitmap_weight(set), buffer, hwloc_bitmap_weight(cset_available));
free(buffer);
/* restore set where it was before the &~ operation above */
hwloc_bitmap_andnot(set, cset_available, set);
}
/* print the smallest object covering the current process binding */
obj = hwloc_get_obj_covering_cpuset(topology, set);
hwloc_obj_type_snprintf(type, sizeof(type), obj, 0);
printf("process is bound within object %s logical index %u\n", type, obj->logical_index);
/* retrieve the single PU where the current thread actually runs within this process binding */
set2 = hwloc_bitmap_alloc();
if (!set2) {
fprintf(stderr, "failed to allocate a bitmap\n");
hwloc_bitmap_free(set);
hwloc_topology_destroy(topology);
return EXIT_FAILURE;
}
err = hwloc_get_last_cpu_location(topology, set2, HWLOC_CPUBIND_THREAD);
if (err < 0) {
fprintf(stderr, "failed to get last cpu location\n");
hwloc_bitmap_free(set);
hwloc_bitmap_free(set2);
hwloc_topology_destroy(topology);
return EXIT_FAILURE;
}
/* sanity checks that are not actually needed but help the reader */
/* this thread runs within the process binding */
assert(hwloc_bitmap_isincluded(set2, set));
/* this thread runs on a single PU at a time */
assert(hwloc_bitmap_weight(set2) == 1);
/* print the logical number of the PU where that thread runs */
/* extract the PU OS index from the bitmap */
i = hwloc_bitmap_first(set2);
obj = hwloc_get_pu_obj_by_os_index(topology, i);
printf("thread is now running on PU logical index %u (OS/physical index %u)\n",
obj->logical_index, i);
/* migrate this single thread to where other PUs within the current binding */
hwloc_bitmap_andnot(set2, set, set2);
err = hwloc_set_cpubind(topology, set2, HWLOC_CPUBIND_THREAD);
if (err < 0) {
fprintf(stderr, "failed to set thread binding\n");
hwloc_bitmap_free(set);
hwloc_bitmap_free(set2);
hwloc_topology_destroy(topology);
return EXIT_FAILURE;
}
/* reprint the PU where that thread runs */
err = hwloc_get_last_cpu_location(topology, set2, HWLOC_CPUBIND_THREAD);
if (err < 0) {
fprintf(stderr, "failed to get last cpu location\n");
hwloc_bitmap_free(set);
hwloc_bitmap_free(set2);
hwloc_topology_destroy(topology);
return EXIT_FAILURE;
}
/* print the logical number of the PU where that thread runs */
/* extract the PU OS index from the bitmap */
i = hwloc_bitmap_first(set2);
obj = hwloc_get_pu_obj_by_os_index(topology, i);
printf("thread is running on PU logical index %u (OS/physical index %u)\n",
obj->logical_index, i);
hwloc_bitmap_free(set);
hwloc_bitmap_free(set2);
/* retrieve the entire set of all PUs */
cset_all = hwloc_topology_get_complete_cpuset(topology);
if (hwloc_bitmap_isequal(cset_all, cset_available)) {
printf("all hardware PUs are available\n");
} else {
printf("only %d hardware PUs are available in the machine among %d\n",
hwloc_bitmap_weight(cset_available), hwloc_bitmap_weight(cset_all));
}
hwloc_topology_destroy(topology);
return EXIT_SUCCESS;
}
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