1#include <errno.h>
2#include <fcntl.h>
3#include <stdio.h>
4#include <stdlib.h>
5#include <string.h>
6#include <sys/mman.h>
7#include <sys/time.h>
8
9#include "pagingtest.h"
10
11#define LINESIZE 32
12
13int thrashing_test(int test_runs) {
14    int fds[4] = {-1, -1, -1, -1};
15    char tmpnames[4][17] = { "thrashing1XXXXXX", "thrashing2XXXXXX", "thrashing3XXXXXX", "thrashing4XXXXXX" };
16    volatile char *bufs[4] = {0};
17    long long k;
18    int ret = -1;
19    struct timeval begin_time, end_time, elapsed_time, total_time;
20    unsigned long long filesize;
21    long num_pages;
22    long pagesize;
23
24    timerclear(&total_time);
25
26    num_pages = sysconf(_SC_PHYS_PAGES);
27    pagesize = sysconf(_SC_PAGE_SIZE);
28    if (num_pages < 0) {
29        fprintf(stderr, "failed to get the number of pages\n");
30        return -1;
31    }
32
33    filesize = num_pages * pagesize / (ARRAY_SIZE(fds) - 1);
34
35    for (size_t i = 0; i < ARRAY_SIZE(fds); i++) {
36        fds[i] = create_tmp_file(tmpnames[i], filesize);
37        if (fds[i] < 0) {
38            goto err_fd;
39        }
40    }
41
42    for (size_t i = 0; i < ARRAY_SIZE(fds); i++) {
43        bufs[i] = mmap(NULL, filesize, PROT_READ, MAP_PRIVATE, fds[i], 0);
44        if (bufs[i] == ((void *)-1)) {
45            fprintf(stderr, "Failed to mmap file: %s\n", strerror(errno));
46            goto err;
47        }
48    }
49
50    for (int i = 0; i < test_runs; i++) {
51        for (size_t j = 0; j < ARRAY_SIZE(fds); j++) {
52            gettimeofday(&begin_time, NULL);
53            //Unfortunately when under memory pressure, fadvise and madvise stop working...
54            //Read backwards to prevent mmap prefetching
55            for (k = ((filesize - 1) & ~(pagesize - 1)); k >= 0; k -= pagesize) {
56                bufs[j][k];
57            }
58            gettimeofday(&end_time, NULL);
59
60            timersub(&end_time, &begin_time, &elapsed_time);
61            timeradd(&total_time, &elapsed_time, &total_time);
62        }
63    }
64
65    printf("thrashing: %llu MB/s\n", (filesize * ARRAY_SIZE(fds) * test_runs * USEC_PER_SEC) /
66             (1024 * 1024 * (total_time.tv_sec * USEC_PER_SEC + total_time.tv_usec)));
67
68    ret = 0;
69
70err:
71    for (size_t i = 0; i < ARRAY_SIZE(bufs) && bufs[i] != NULL; i++) {
72        munmap((void *)bufs[i], filesize);
73    }
74err_fd:
75    for (size_t i = 0; i < ARRAY_SIZE(fds) && fds[i] >= 0; i++) {
76        close(fds[i]);
77    }
78    return ret;
79}
80