src/common/vmfill.c

   1 #include <stdint.h>
   2 #include <sys/mman.h>
   3 #include <fcntl.h>
   4 #include <unistd.h>
   5 #include <limits.h>
   6 #include "test.h"
   7 #ifndef PAGE_SIZE
   8         #define PAGE_SIZE sysconf(_SC_PAGE_SIZE)
   9 #endif
  10 #ifndef MAP_ANONYMOUS
  11         #define MAP_ANONYMOUS 0
  12 #endif
  13
  14 /* max mmap size, *start is the largest power-of-2 size considered */
  15 static size_t mmax(int fd, size_t *start)
  16 {
  17         size_t i, n;
  18         void *p;
  19
  20         for (i=n=*start; i>=PAGE_SIZE; i/=2) {
  21                 if ((p=mmap(0, n, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, fd, 0)) == MAP_FAILED) {
  22                         n -= i/2;
  23                 } else {
  24                         munmap(p, n);
  25                         if (n == i)
  26                                 *start = n;
  27                         n += i/2;
  28                 }
  29         }
  30         return n & -PAGE_SIZE;
  31 }
  32
  33 /*
  34 fills the virtual memory with anonymous PROT_NONE mmaps,
  35 returns the mappings in *p and *n in decreasing size order,
  36 the return value is the number of mappings or -1 on failure.
  37 */
  38 int t_vmfill(void **p, size_t *n, int len)
  39 {
  40         int fd = MAP_ANONYMOUS ? -1 : open("/dev/zero", O_RDWR);
  41         size_t start = SIZE_MAX/2 + 1;
  42         size_t m;
  43         void *q;
  44         int i;
  45
  46         for (i=0;;i++) {
  47                 m = mmax(fd, &start);
  48                 if (!m)
  49                         break;
  50                 q = mmap(0, m, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, fd, 0);
  51                 if (q == MAP_FAILED)
  52                         return -1;
  53                 if (i < len) {
  54                         p[i] = q;
  55                         n[i] = m;
  56                 }
  57         }
  58         return i;
  59 }