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/* This example program plays with:
* - finding local NUMA nodes
* - finding the best NUMA nodes for bandwidth/latency
* - displaying the bandwidth/latency values of NUMA nodes
* - allocating on the best NUMA node for bandwidth
*
* Copyright © 2022 Inria. All rights reserved.
* See COPYING in top-level directory.
*/
#include "hwloc.h"
#include <errno.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
hwloc_topology_t topology;
hwloc_obj_t core, *nodes, bestnode;
struct hwloc_location initiator;
unsigned i,n;
char *s, *buffer;
int err;
/* Allocate, initialize and load topology object. */
hwloc_topology_init(&topology);
hwloc_topology_load(topology);
/* Find max number of NUMA nodes to allocate the array for hwloc_get_local_numanode_objs() */
n = hwloc_bitmap_weight(hwloc_topology_get_topology_nodeset(topology));
printf("There are %u NUMA nodes\n", n);
nodes = malloc(n * sizeof(*nodes));
assert(nodes);
/* Take the first core */
core = hwloc_get_obj_by_type(topology, HWLOC_OBJ_CORE, 0);
if (!core)
goto out;
hwloc_bitmap_asprintf(&s, core->cpuset);
printf("Core L#0 cpuset = %s\n", s);
free(s);
/* setup the initiator to the first core cpuset */
initiator.type = HWLOC_LOCATION_TYPE_CPUSET;
initiator.location.cpuset = core->cpuset;
/* get local NUMA nodes and display their attributes */
err = hwloc_get_local_numanode_objs(topology, &initiator, &n, nodes,
/* we want NUMA nodes that are local to that core or to more */
HWLOC_LOCAL_NUMANODE_FLAG_LARGER_LOCALITY);
printf("Found %u local NUMA nodes\n", n);
for(i=0; i<n; i++) {
hwloc_uint64_t latency, bandwidth;
printf("NUMA node L#%u P#%u (subtype %s) is local to core L#0\n", nodes[i]->logical_index, nodes[i]->os_index, nodes[i]->subtype);
err = hwloc_memattr_get_value(topology, HWLOC_MEMATTR_ID_BANDWIDTH, nodes[i], &initiator, 0, &bandwidth);
if (err < 0) {
printf(" bandwidth is unknown\n");
} else {
printf(" bandwidth = %llu MiB/s\n", (unsigned long long) bandwidth);
}
err = hwloc_memattr_get_value(topology, HWLOC_MEMATTR_ID_LATENCY, nodes[i], &initiator, 0, &latency);
if (err < 0) {
printf(" latency is unknown\n");
} else {
printf(" latency = %llu ns\n", (unsigned long long) latency);
}
}
free(nodes);
/* allocate on best-bandwidth node */
err = hwloc_memattr_get_best_target(topology, HWLOC_MEMATTR_ID_BANDWIDTH, &initiator, 0, &bestnode, NULL);
if (err < 0) {
printf("Couldn't find best NUMA node for bandwidth to core L#0\n");
} else {
printf("Best bandwidth NUMA node for core L#0 is L#%u P#%u\n", bestnode->logical_index, bestnode->os_index);
/* allocate memory on best node */
buffer = hwloc_alloc_membind(topology, 1048576, bestnode->nodeset, HWLOC_MEMBIND_BIND, HWLOC_MEMBIND_BYNODESET);
printf("Allocated buffer %p on best node\n", buffer);
free(buffer);
}
out:
/* Destroy topology object. */
hwloc_topology_destroy(topology);
return 0;
}
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