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#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <unistd.h>
void* alloc_set(size_t size) {
void* addr = NULL;
addr = malloc(size);
if (!addr) {
printf("Allocating %zd MB failed\n", size / 1024 / 1024);
} else {
memset(addr, 0, size);
}
return addr;
}
void add_pressure(size_t* shared, size_t size, size_t step_size, size_t duration,
const char* oom_score) {
int fd, ret;
fd = open("/proc/self/oom_score_adj", O_WRONLY);
ret = write(fd, oom_score, strlen(oom_score));
if (ret < 0) {
printf("Writing oom_score_adj failed with err %s\n", strerror(errno));
}
close(fd);
if (alloc_set(size)) {
*shared = size;
}
while (alloc_set(step_size)) {
size += step_size;
*shared = size;
usleep(duration);
}
}
void usage() {
printf("Usage: [OPTIONS]\n\n"
" -d N: Duration in microsecond to sleep between each allocation.\n"
" -i N: Number of iterations to run the alloc process.\n"
" -o N: The oom_score to set the child process to before alloc.\n"
" -s N: Number of bytes to allocate in an alloc process loop.\n");
}
int main(int argc, char* argv[]) {
pid_t pid;
size_t* shared;
int c, i = 0;
size_t duration = 1000;
int iterations = 0;
const char* oom_score = "899";
size_t step_size = 2 * 1024 * 1024; // 2 MB
size_t size = step_size;
while ((c = getopt(argc, argv, "hi:d:o:s:")) != -1) {
switch (c) {
case 'i':
iterations = atoi(optarg);
break;
case 'd':
duration = atoi(optarg);
break;
case 'o':
oom_score = optarg;
break;
case 's':
step_size = atoi(optarg);
break;
case 'h':
usage();
abort();
default:
abort();
}
}
shared = (size_t*)mmap(NULL, sizeof(size_t), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED,
0, 0);
while (iterations == 0 || i < iterations) {
*shared = 0;
pid = fork();
if (!pid) {
/* Child */
add_pressure(shared, size, step_size, duration, oom_score);
/* Shoud not get here */
exit(0);
} else {
wait(NULL);
printf("Child %d allocated %zd MB\n", i, *shared / 1024 / 1024);
size = *shared / 2;
}
i++;
}
}
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