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/* pcount PID: count user-mode instructions and cycles of every thread of
* PID from "ready" (on stderr) until stdin closes; prints them as JSON.
* perf_event_open alone: a perf_event_paranoid of 2 allows it for one's own
* processes, and no perf tool is needed. */
#define _GNU_SOURCE
#include <dirent.h>
#include <linux/perf_event.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <unistd.h>
static int open_counter(pid_t tid, uint64_t config) {
struct perf_event_attr attr;
memset(&attr, 0, sizeof(attr));
attr.size = sizeof(attr);
attr.type = PERF_TYPE_HARDWARE;
attr.config = config;
attr.disabled = 1;
attr.exclude_kernel = 1;
attr.exclude_hv = 1;
return (int)syscall(SYS_perf_event_open, &attr, tid, -1, -1, 0);
}
int main(int argc, char **argv) {
if (argc != 2) return 2;
char path[64];
snprintf(path, sizeof(path), "/proc/%s/task", argv[1]);
DIR *dir = opendir(path);
if (!dir) { perror("opendir"); return 1; }
int fds[512][2], n = 0;
struct dirent *e;
while ((e = readdir(dir)) && n < 512) {
if (e->d_name[0] == '.') continue;
pid_t tid = atoi(e->d_name);
fds[n][0] = open_counter(tid, PERF_COUNT_HW_INSTRUCTIONS);
fds[n][1] = open_counter(tid, PERF_COUNT_HW_CPU_CYCLES);
if (fds[n][0] < 0 || fds[n][1] < 0) { perror("perf_event_open"); return 1; }
++n;
}
closedir(dir);
for (int i = 0; i < n; ++i) for (int k = 0; k < 2; ++k) ioctl(fds[i][k], PERF_EVENT_IOC_RESET, 0), ioctl(fds[i][k], PERF_EVENT_IOC_ENABLE, 0);
fprintf(stderr, "ready\n");
char buffer[64];
while (fread(buffer, 1, sizeof(buffer), stdin) > 0) {}
uint64_t total[2] = {0, 0};
for (int i = 0; i < n; ++i)
for (int k = 0; k < 2; ++k) {
uint64_t v = 0;
ioctl(fds[i][k], PERF_EVENT_IOC_DISABLE, 0);
if (read(fds[i][k], &v, sizeof(v)) == sizeof(v)) total[k] += v;
}
printf("{\"threads\": %d, \"instructions\": %llu, \"cycles\": %llu}\n", n, (unsigned long long)total[0], (unsigned long long)total[1]);
return 0;
}
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