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