Based on kernel version 3.3. Page generated on 2012-03-23 21:41 EST.
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 34 static void check_bytes(char *addr) 35 { 36 printf("First hex is %x\n", *((unsigned int *)addr)); 37 } 38 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 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 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 }