*******************************************************************
/*
- * Example of using huge page memory in a user application using Sys V shared
- * memory system calls. In this example the app is requesting 256MB of
- * memory that is backed by huge pages. The application uses the flag
- * SHM_HUGETLB in the shmget system call to inform the kernel that it is
- * requesting huge pages.
- *
- * For the ia64 architecture, the Linux kernel reserves Region number 4 for
- * huge pages. That means that if one requires a fixed address, a huge page
- * aligned address starting with 0x800000... will be required. If a fixed
- * address is not required, the kernel will select an address in the proper
- * range.
- * Other architectures, such as ppc64, i386 or x86_64 are not so constrained.
- *
- * Note: The default shared memory limit is quite low on many kernels,
- * you may need to increase it via:
- *
- * echo 268435456 > /proc/sys/kernel/shmmax
- *
- * This will increase the maximum size per shared memory segment to 256MB.
- * The other limit that you will hit eventually is shmall which is the
- * total amount of shared memory in pages. To set it to 16GB on a system
- * with a 4kB pagesize do:
- *
- * echo 4194304 > /proc/sys/kernel/shmall
+ * hugepage-shm: see Documentation/vm/hugepage-shm.c
*/
-#include <stdlib.h>
-#include <stdio.h>
-#include <sys/types.h>
-#include <sys/ipc.h>
-#include <sys/shm.h>
-#include <sys/mman.h>
-
-#ifndef SHM_HUGETLB
-#define SHM_HUGETLB 04000
-#endif
-
-#define LENGTH (256UL*1024*1024)
-
-#define dprintf(x) printf(x)
-
-#define ADDR (void *)(0x0UL) /* let kernel choose address */
-#define SHMAT_FLAGS (0)
-
-int main(void)
-{
- int shmid;
- unsigned long i;
- char *shmaddr;
-
- if ((shmid = shmget(2, LENGTH,
- SHM_HUGETLB | IPC_CREAT | SHM_R | SHM_W)) < 0) {
- perror("shmget");
- exit(1);
- }
- printf("shmid: 0x%x\n", shmid);
-
- shmaddr = shmat(shmid, ADDR, SHMAT_FLAGS);
- if (shmaddr == (char *)-1) {
- perror("Shared memory attach failure");
- shmctl(shmid, IPC_RMID, NULL);
- exit(2);
- }
- printf("shmaddr: %p\n", shmaddr);
-
- dprintf("Starting the writes:\n");
- for (i = 0; i < LENGTH; i++) {
- shmaddr[i] = (char)(i);
- if (!(i % (1024 * 1024)))
- dprintf(".");
- }
- dprintf("\n");
-
- dprintf("Starting the Check...");
- for (i = 0; i < LENGTH; i++)
- if (shmaddr[i] != (char)i)
- printf("\nIndex %lu mismatched\n", i);
- dprintf("Done.\n");
-
- if (shmdt((const void *)shmaddr) != 0) {
- perror("Detach failure");
- shmctl(shmid, IPC_RMID, NULL);
- exit(3);
- }
-
- shmctl(shmid, IPC_RMID, NULL);
-
- return 0;
-}
*******************************************************************
/*
- * Example of using huge page memory in a user application using the mmap
- * system call. Before running this application, make sure that the
- * administrator has mounted the hugetlbfs filesystem (on some directory
- * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this
- * example, the app is requesting memory of size 256MB that is backed by
- * huge pages.
- *
- * For the ia64 architecture, the Linux kernel reserves Region number 4 for
- * huge pages. That means that if one requires a fixed address, a huge page
- * aligned address starting with 0x800000... will be required. If a fixed
- * address is not required, the kernel will select an address in the proper
- * range.
- * Other architectures, such as ppc64, i386 or x86_64 are not so constrained.
+ * hugepage-mmap: see Documentation/vm/hugepage-mmap.c
*/
-#include <stdlib.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <sys/mman.h>
-#include <fcntl.h>
-
-#define FILE_NAME "/mnt/hugepagefile"
-#define LENGTH (256UL*1024*1024)
-#define PROTECTION (PROT_READ | PROT_WRITE)
-
-#define ADDR (void *)(0x0UL) /* let kernel choose address */
-#define FLAGS (MAP_SHARED)
-
-void check_bytes(char *addr)
-{
- printf("First hex is %x\n", *((unsigned int *)addr));
-}
-
-void write_bytes(char *addr)
-{
- unsigned long i;
-
- for (i = 0; i < LENGTH; i++)
- *(addr + i) = (char)i;
-}
-
-void read_bytes(char *addr)
-{
- unsigned long i;
-
- check_bytes(addr);
- for (i = 0; i < LENGTH; i++)
- if (*(addr + i) != (char)i) {
- printf("Mismatch at %lu\n", i);
- break;
- }
-}
-
-int main(void)
-{
- void *addr;
- int fd;
-
- fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755);
- if (fd < 0) {
- perror("Open failed");
- exit(1);
- }
-
- addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0);
- if (addr == MAP_FAILED) {
- perror("mmap");
- unlink(FILE_NAME);
- exit(1);
- }
-
- printf("Returned address is %p\n", addr);
- check_bytes(addr);
- write_bytes(addr);
- read_bytes(addr);
-
- munmap(addr, LENGTH);
- close(fd);
- unlink(FILE_NAME);
-
- return 0;
-}
projects / cascardo / linux.git / blobdiff