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/*
* usemem.c exercises the ksm.c file in the mm for hugepages
*
* It takes one argument 'size' and mmaps anonymous memory of 'size'
*
* into the process virtual address space. The allocated memory is made mergeable
*
* to make ksm scan it. The MADV_HUGEPAGE flag makes sure that the pages are hugepages
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#define SLEEP_TIME 60
void usage(char *name)
{
fprintf(stderr, "usage: %s SIZE\n", name);
exit(1);
}
/* calls madvise with the the specified flag */
void call_madvise(unsigned char *pointer_to_address, unsigned long size, int advise)
{
if ((madvise(pointer_to_address, size, advise)) == -1) {
fprintf(stderr, "madvise failed with error : %s\n", strerror(errno));
munmap(pointer_to_address, size);
exit(1);
}
}
int main(int argc, char *argv[])
{
if (argc != 2) usage(argv[0]);
unsigned long size = atoi(argv[1]);
unsigned char *p;
char command[50];
p = mmap(NULL, size, PROT_READ|PROT_WRITE,
MAP_POPULATE|MAP_ANON|MAP_PRIVATE, -1, 0);
if (p == MAP_FAILED) {
fprintf(stderr, "anon mmap failed: %s\n", strerror(errno));
exit(1);
}
/* collapse the pages into hugepages */
call_madvise(p, size, MADV_HUGEPAGE);
/* wait for hugepages to be allocated */
sleep(30);
/* make pages mergeable advised */
call_madvise(p, size, MADV_MERGEABLE);
sleep(30);
/* Turn off ksm and unmerge shared memory */
sprintf(command, "echo 2 > /sys/kernel/mm/ksm/run");
system(command);
/* make pages unmergeable */
call_madvise(p, size, MADV_UNMERGEABLE);
/* unmap mapping */
munmap(p, size);
return 0;
}
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