diff options
Diffstat (limited to 'Documentation/vm/hugetlbpage.txt')
-rw-r--r-- | Documentation/vm/hugetlbpage.txt | 169 |
1 files changed, 2 insertions, 167 deletions
diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt index bc31636973e3..457634c1e03e 100644 --- a/Documentation/vm/hugetlbpage.txt +++ b/Documentation/vm/hugetlbpage.txt | |||
@@ -299,176 +299,11 @@ map_hugetlb.c. | |||
299 | ******************************************************************* | 299 | ******************************************************************* |
300 | 300 | ||
301 | /* | 301 | /* |
302 | * Example of using huge page memory in a user application using Sys V shared | 302 | * hugepage-shm: see Documentation/vm/hugepage-shm.c |
303 | * memory system calls. In this example the app is requesting 256MB of | ||
304 | * memory that is backed by huge pages. The application uses the flag | ||
305 | * SHM_HUGETLB in the shmget system call to inform the kernel that it is | ||
306 | * requesting huge pages. | ||
307 | * | ||
308 | * For the ia64 architecture, the Linux kernel reserves Region number 4 for | ||
309 | * huge pages. That means that if one requires a fixed address, a huge page | ||
310 | * aligned address starting with 0x800000... will be required. If a fixed | ||
311 | * address is not required, the kernel will select an address in the proper | ||
312 | * range. | ||
313 | * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. | ||
314 | * | ||
315 | * Note: The default shared memory limit is quite low on many kernels, | ||
316 | * you may need to increase it via: | ||
317 | * | ||
318 | * echo 268435456 > /proc/sys/kernel/shmmax | ||
319 | * | ||
320 | * This will increase the maximum size per shared memory segment to 256MB. | ||
321 | * The other limit that you will hit eventually is shmall which is the | ||
322 | * total amount of shared memory in pages. To set it to 16GB on a system | ||
323 | * with a 4kB pagesize do: | ||
324 | * | ||
325 | * echo 4194304 > /proc/sys/kernel/shmall | ||
326 | */ | 303 | */ |
327 | #include <stdlib.h> | ||
328 | #include <stdio.h> | ||
329 | #include <sys/types.h> | ||
330 | #include <sys/ipc.h> | ||
331 | #include <sys/shm.h> | ||
332 | #include <sys/mman.h> | ||
333 | |||
334 | #ifndef SHM_HUGETLB | ||
335 | #define SHM_HUGETLB 04000 | ||
336 | #endif | ||
337 | |||
338 | #define LENGTH (256UL*1024*1024) | ||
339 | |||
340 | #define dprintf(x) printf(x) | ||
341 | |||
342 | #define ADDR (void *)(0x0UL) /* let kernel choose address */ | ||
343 | #define SHMAT_FLAGS (0) | ||
344 | |||
345 | int main(void) | ||
346 | { | ||
347 | int shmid; | ||
348 | unsigned long i; | ||
349 | char *shmaddr; | ||
350 | |||
351 | if ((shmid = shmget(2, LENGTH, | ||
352 | SHM_HUGETLB | IPC_CREAT | SHM_R | SHM_W)) < 0) { | ||
353 | perror("shmget"); | ||
354 | exit(1); | ||
355 | } | ||
356 | printf("shmid: 0x%x\n", shmid); | ||
357 | |||
358 | shmaddr = shmat(shmid, ADDR, SHMAT_FLAGS); | ||
359 | if (shmaddr == (char *)-1) { | ||
360 | perror("Shared memory attach failure"); | ||
361 | shmctl(shmid, IPC_RMID, NULL); | ||
362 | exit(2); | ||
363 | } | ||
364 | printf("shmaddr: %p\n", shmaddr); | ||
365 | |||
366 | dprintf("Starting the writes:\n"); | ||
367 | for (i = 0; i < LENGTH; i++) { | ||
368 | shmaddr[i] = (char)(i); | ||
369 | if (!(i % (1024 * 1024))) | ||
370 | dprintf("."); | ||
371 | } | ||
372 | dprintf("\n"); | ||
373 | |||
374 | dprintf("Starting the Check..."); | ||
375 | for (i = 0; i < LENGTH; i++) | ||
376 | if (shmaddr[i] != (char)i) | ||
377 | printf("\nIndex %lu mismatched\n", i); | ||
378 | dprintf("Done.\n"); | ||
379 | |||
380 | if (shmdt((const void *)shmaddr) != 0) { | ||
381 | perror("Detach failure"); | ||
382 | shmctl(shmid, IPC_RMID, NULL); | ||
383 | exit(3); | ||
384 | } | ||
385 | |||
386 | shmctl(shmid, IPC_RMID, NULL); | ||
387 | |||
388 | return 0; | ||
389 | } | ||
390 | 304 | ||
391 | ******************************************************************* | 305 | ******************************************************************* |
392 | 306 | ||
393 | /* | 307 | /* |
394 | * Example of using huge page memory in a user application using the mmap | 308 | * hugepage-mmap: see Documentation/vm/hugepage-mmap.c |
395 | * system call. Before running this application, make sure that the | ||
396 | * administrator has mounted the hugetlbfs filesystem (on some directory | ||
397 | * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this | ||
398 | * example, the app is requesting memory of size 256MB that is backed by | ||
399 | * huge pages. | ||
400 | * | ||
401 | * For the ia64 architecture, the Linux kernel reserves Region number 4 for | ||
402 | * huge pages. That means that if one requires a fixed address, a huge page | ||
403 | * aligned address starting with 0x800000... will be required. If a fixed | ||
404 | * address is not required, the kernel will select an address in the proper | ||
405 | * range. | ||
406 | * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. | ||
407 | */ | 309 | */ |
408 | #include <stdlib.h> | ||
409 | #include <stdio.h> | ||
410 | #include <unistd.h> | ||
411 | #include <sys/mman.h> | ||
412 | #include <fcntl.h> | ||
413 | |||
414 | #define FILE_NAME "/mnt/hugepagefile" | ||
415 | #define LENGTH (256UL*1024*1024) | ||
416 | #define PROTECTION (PROT_READ | PROT_WRITE) | ||
417 | |||
418 | #define ADDR (void *)(0x0UL) /* let kernel choose address */ | ||
419 | #define FLAGS (MAP_SHARED) | ||
420 | |||
421 | void check_bytes(char *addr) | ||
422 | { | ||
423 | printf("First hex is %x\n", *((unsigned int *)addr)); | ||
424 | } | ||
425 | |||
426 | void write_bytes(char *addr) | ||
427 | { | ||
428 | unsigned long i; | ||
429 | |||
430 | for (i = 0; i < LENGTH; i++) | ||
431 | *(addr + i) = (char)i; | ||
432 | } | ||
433 | |||
434 | void read_bytes(char *addr) | ||
435 | { | ||
436 | unsigned long i; | ||
437 | |||
438 | check_bytes(addr); | ||
439 | for (i = 0; i < LENGTH; i++) | ||
440 | if (*(addr + i) != (char)i) { | ||
441 | printf("Mismatch at %lu\n", i); | ||
442 | break; | ||
443 | } | ||
444 | } | ||
445 | |||
446 | int main(void) | ||
447 | { | ||
448 | void *addr; | ||
449 | int fd; | ||
450 | |||
451 | fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755); | ||
452 | if (fd < 0) { | ||
453 | perror("Open failed"); | ||
454 | exit(1); | ||
455 | } | ||
456 | |||
457 | addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0); | ||
458 | if (addr == MAP_FAILED) { | ||
459 | perror("mmap"); | ||
460 | unlink(FILE_NAME); | ||
461 | exit(1); | ||
462 | } | ||
463 | |||
464 | printf("Returned address is %p\n", addr); | ||
465 | check_bytes(addr); | ||
466 | write_bytes(addr); | ||
467 | read_bytes(addr); | ||
468 | |||
469 | munmap(addr, LENGTH); | ||
470 | close(fd); | ||
471 | unlink(FILE_NAME); | ||
472 | |||
473 | return 0; | ||
474 | } | ||