summaryrefslogtreecommitdiffstats
path: root/Documentation/vm/map_hugetlb.c
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/vm/map_hugetlb.c')
-rw-r--r--Documentation/vm/map_hugetlb.c77
1 files changed, 77 insertions, 0 deletions
diff --git a/Documentation/vm/map_hugetlb.c b/Documentation/vm/map_hugetlb.c
new file mode 100644
index 000000000000..e2bdae37f499
--- /dev/null
+++ b/Documentation/vm/map_hugetlb.c
@@ -0,0 +1,77 @@
+/*
+ * Example of using hugepage memory in a user application using the mmap
+ * system call with MAP_HUGETLB flag. Before running this program make
+ * sure the administrator has allocated enough default sized huge pages
+ * to cover the 256 MB allocation.
+ *
+ * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
+ * That means the addresses starting with 0x800000... will need to be
+ * specified. Specifying a fixed address is not required on ppc64, i386
+ * or x86_64.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+
+#define LENGTH (256UL*1024*1024)
+#define PROTECTION (PROT_READ | PROT_WRITE)
+
+#ifndef MAP_HUGETLB
+#define MAP_HUGETLB 0x40
+#endif
+
+/* Only ia64 requires this */
+#ifdef __ia64__
+#define ADDR (void *)(0x8000000000000000UL)
+#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
+#else
+#define ADDR (void *)(0x0UL)
+#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
+#endif
+
+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;
+
+ addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, 0, 0);
+ if (addr == MAP_FAILED) {
+ perror("mmap");
+ exit(1);
+ }
+
+ printf("Returned address is %p\n", addr);
+ check_bytes(addr);
+ write_bytes(addr);
+ read_bytes(addr);
+
+ munmap(addr, LENGTH);
+
+ return 0;
+}