1 /*
2 * Example of using hugepage memory in a user application using the mmap
3 * system call with MAP_HUGETLB flag. Before running this program make
4 * sure the administrator has allocated enough default sized huge pages
5 * to cover the 256 MB allocation.
6 *
7 * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
8 * That means the addresses starting with 0x800000... will need to be
9 * specified. Specifying a fixed address is not required on ppc64, i386
10 * or x86_64.
11 */
12 #include <stdlib.h>
13 #include <stdio.h>
14 #include <unistd.h>
15 #include <sys/mman.h>
16 #include <fcntl.h>
17
18 #define LENGTH (256UL*1024*1024)
19 #define PROTECTION (PROT_READ | PROT_WRITE)
20
21 #ifndef MAP_HUGETLB
22 #define MAP_HUGETLB 0x40000 /* arch specific */
23 #endif
24
25 /* Only ia64 requires this */
26 #ifdef __ia64__
27 #define ADDR (void *)(0x8000000000000000UL)
28 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
29 #else
30 #define ADDR (void *)(0x0UL)
31 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
32 #endif
33
check_bytes(char * addr)34 static void check_bytes(char *addr)
35 {
36 printf("First hex is %x\n", *((unsigned int *)addr));
37 }
38
write_bytes(char * addr)39 static void write_bytes(char *addr)
40 {
41 unsigned long i;
42
43 for (i = 0; i < LENGTH; i++)
44 *(addr + i) = (char)i;
45 }
46
read_bytes(char * addr)47 static void read_bytes(char *addr)
48 {
49 unsigned long i;
50
51 check_bytes(addr);
52 for (i = 0; i < LENGTH; i++)
53 if (*(addr + i) != (char)i) {
54 printf("Mismatch at %lu\n", i);
55 break;
56 }
57 }
58
main(void)59 int main(void)
60 {
61 void *addr;
62
63 addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, 0, 0);
64 if (addr == MAP_FAILED) {
65 perror("mmap");
66 exit(1);
67 }
68
69 printf("Returned address is %p\n", addr);
70 check_bytes(addr);
71 write_bytes(addr);
72 read_bytes(addr);
73
74 munmap(addr, LENGTH);
75
76 return 0;
77 }
78