Randy Dunlap | 70bace8 | 2010-03-10 15:21:58 -0800 | [diff] [blame] | 1 | /* |
| 2 | * hugepage-mmap: |
| 3 | * |
| 4 | * Example of using huge page memory in a user application using the mmap |
| 5 | * system call. Before running this application, make sure that the |
| 6 | * administrator has mounted the hugetlbfs filesystem (on some directory |
| 7 | * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this |
| 8 | * example, the app is requesting memory of size 256MB that is backed by |
| 9 | * huge pages. |
| 10 | * |
| 11 | * For the ia64 architecture, the Linux kernel reserves Region number 4 for |
| 12 | * huge pages. That means that if one requires a fixed address, a huge page |
| 13 | * aligned address starting with 0x800000... will be required. If a fixed |
| 14 | * address is not required, the kernel will select an address in the proper |
| 15 | * range. |
| 16 | * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. |
| 17 | */ |
| 18 | |
| 19 | #include <stdlib.h> |
| 20 | #include <stdio.h> |
| 21 | #include <unistd.h> |
| 22 | #include <sys/mman.h> |
| 23 | #include <fcntl.h> |
| 24 | |
| 25 | #define FILE_NAME "/mnt/hugepagefile" |
| 26 | #define LENGTH (256UL*1024*1024) |
| 27 | #define PROTECTION (PROT_READ | PROT_WRITE) |
| 28 | |
| 29 | /* Only ia64 requires this */ |
| 30 | #ifdef __ia64__ |
| 31 | #define ADDR (void *)(0x8000000000000000UL) |
| 32 | #define FLAGS (MAP_SHARED | MAP_FIXED) |
| 33 | #else |
| 34 | #define ADDR (void *)(0x0UL) |
| 35 | #define FLAGS (MAP_SHARED) |
| 36 | #endif |
| 37 | |
| 38 | static void check_bytes(char *addr) |
| 39 | { |
| 40 | printf("First hex is %x\n", *((unsigned int *)addr)); |
| 41 | } |
| 42 | |
| 43 | static void write_bytes(char *addr) |
| 44 | { |
| 45 | unsigned long i; |
| 46 | |
| 47 | for (i = 0; i < LENGTH; i++) |
| 48 | *(addr + i) = (char)i; |
| 49 | } |
| 50 | |
| 51 | static void read_bytes(char *addr) |
| 52 | { |
| 53 | unsigned long i; |
| 54 | |
| 55 | check_bytes(addr); |
| 56 | for (i = 0; i < LENGTH; i++) |
| 57 | if (*(addr + i) != (char)i) { |
| 58 | printf("Mismatch at %lu\n", i); |
| 59 | break; |
| 60 | } |
| 61 | } |
| 62 | |
| 63 | int main(void) |
| 64 | { |
| 65 | void *addr; |
| 66 | int fd; |
| 67 | |
| 68 | fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755); |
| 69 | if (fd < 0) { |
| 70 | perror("Open failed"); |
| 71 | exit(1); |
| 72 | } |
| 73 | |
| 74 | addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0); |
| 75 | if (addr == MAP_FAILED) { |
| 76 | perror("mmap"); |
| 77 | unlink(FILE_NAME); |
| 78 | exit(1); |
| 79 | } |
| 80 | |
| 81 | printf("Returned address is %p\n", addr); |
| 82 | check_bytes(addr); |
| 83 | write_bytes(addr); |
| 84 | read_bytes(addr); |
| 85 | |
| 86 | munmap(addr, LENGTH); |
| 87 | close(fd); |
| 88 | unlink(FILE_NAME); |
| 89 | |
| 90 | return 0; |
| 91 | } |