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Bind epoll_loop to last online CPU #73

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a7c29e0
Bind `epoll_loop` to last online CPU
li041 Jan 26, 2026
a1f00a4
need to be squashed into prev commit
li041 Jan 28, 2026
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29 changes: 29 additions & 0 deletions tools/event_monitor.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,10 @@
 * Authors:
 *      Guowei Li <2401213322@stu.pku.edu.cn>
 */
#define _GNU_SOURCE
#include <errno.h>
#include <pthread.h>
#include <sched.h>
#include <stdlib.h>
#include <unistd.h>

Expand Down Expand Up @@ -81,6 +83,33 @@ int initialize_event_monitor() {
epoll_fd = epoll_create1(0);
log_debug("create epoll_fd %d", epoll_fd);
pthread_create(&emonitor_tid, NULL, epoll_loop, NULL);
cpu_set_t cpuset;
CPU_ZERO(&cpuset);
if (sched_getaffinity(0, sizeof(cpu_set_t), &cpuset) == 0) {
int last_cpu = -1;
for (int i = CPU_SETSIZE - 1; i >= 1; i--) {
if (CPU_ISSET(i, &cpuset)) {
last_cpu = i;
break;
}
}

if (last_cpu != -1) {
cpu_set_t set;
CPU_ZERO(&set);
CPU_SET(last_cpu, &set);
if (pthread_setaffinity_np(emonitor_tid, sizeof(cpu_set_t), &set) !=
0) {
log_warn("failed to set epoll_loop thread to cpu %d", last_cpu);
} else {
log_info("epoll_loop thread set to cpu %d", last_cpu);
}
} else {
log_warn("No available CPU other than CPU0");
}
} else {
log_warn("failed to get cpu affinity: %d", errno);
}
if (epoll_fd >= 0)
return 0;
else {
Expand Down