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70bace8c RD |
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 | } |