106 lines
2.2 KiB
C
106 lines
2.2 KiB
C
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <stdint.h>
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#include <assert.h>
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int main(void)
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{
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const char *filename = "test.bin";
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/* Ouverture du fichier */
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int fd = open(filename, O_RDONLY);
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assert( fd != -1);
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/* Taille du fichier */
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struct stat st;
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assert( fstat(fd, &st) != -1);
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size_t filesize = st.st_size;
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/* Taille d'une page mémoire */
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long pagesize = sysconf(_SC_PAGESIZE);
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assert(pagesize != -1);
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/* Nombre de pages nécessaires pour mapper le fichier */
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size_t npages = (filesize + pagesize - 1) / pagesize;
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printf("Taille du fichier : %zu octets\n", filesize);
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printf("Taille d'une page : %ld octets\n", pagesize);
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printf("Nombre de pages : %zu\n", npages);
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posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
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/* Création du mapping */
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unsigned char *p = mmap(NULL, filesize,
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PROT_READ,
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MAP_PRIVATE,
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fd, 0);
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assert(p != MAP_FAILED);
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madvise(p, filesize, MADV_RANDOM);
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close(fd);
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/*
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* Tableau utilisé par mincore().
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* Un octet par page.
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*/
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unsigned char *vec = malloc(npages);
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assert( vec != NULL);
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/*
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* Interrogation initiale de la résidence des pages.
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*/
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assert(mincore(p, filesize, vec) != -1);
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size_t resident = 0;
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for (size_t i = 0; i < npages; i++) {
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if (vec[i] & 1)
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resident++;
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}
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printf("\nPages résidentes initialement : %zu / %zu\n",
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resident, npages);
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printf("\nAppuyez sur Entrée pour accéder à p[0]...");
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getchar();
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/*
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* Accès à la première page.
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*/
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volatile unsigned char x = p[0];
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printf("Valeur lue : %u\n", x);
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/*
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* Nouvelle interrogation.
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*/
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assert(mincore(p, filesize, vec) != -1);
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resident = 0;
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for (size_t i = 0; i < npages; i++) {
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if (vec[i] & 1)
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resident++;
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}
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printf("Pages résidentes après p[0] : %zu / %zu\n",
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resident, npages);
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free(vec);
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munmap(p, filesize);
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return EXIT_SUCCESS;
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}
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