---

yaml
---
r: 187199
b: refs/heads/master
c: 70bace8
h: refs/heads/master
i:
  187197: ef78ae9
  187195: 11d79b5
  187191: 809a33f
  187183: 4cc2f73
  187167: 37eaa85
  187135: 4abfb74
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1e0051ae48a253685e4309256f9c1ec2bdb74b5d
+refs/heads/master: 70bace8c1edefa700c7f7af522c5374ef63860ae

trunk/Documentation/vm/00-INDEX

@@ -4,23 +4,35 @@ active_mm.txt
 	- An explanation from Linus about tsk->active_mm vs tsk->mm.
 balance
 	- various information on memory balancing.
+hugepage-mmap.c
+	- Example app using huge page memory with the mmap system call.
+hugepage-shm.c
+	- Example app using huge page memory with Sys V shared memory system calls.
 hugetlbpage.txt
 	- a brief summary of hugetlbpage support in the Linux kernel.
+hwpoison.txt
+	- explains what hwpoison is
 ksm.txt
 	- how to use the Kernel Samepage Merging feature.
 locking
 	- info on how locking and synchronization is done in the Linux vm code.
+map_hugetlb.c
+	- an example program that uses the MAP_HUGETLB mmap flag.
 numa
 	- information about NUMA specific code in the Linux vm.
 numa_memory_policy.txt
 	- documentation of concepts and APIs of the 2.6 memory policy support.
 overcommit-accounting
 	- description of the Linux kernels overcommit handling modes.
+page-types.c
+	- Tool for querying page flags
 page_migration
 	- description of page migration in NUMA systems.
+pagemap.txt
+	- pagemap, from the userspace perspective
 slabinfo.c
 	- source code for a tool to get reports about slabs.
 slub.txt
 	- a short users guide for SLUB.
-map_hugetlb.c
-	- an example program that uses the MAP_HUGETLB mmap flag.
+unevictable-lru.txt
+	- Unevictable LRU infrastructure

trunk/Documentation/vm/Makefile

@@ -2,7 +2,7 @@
 obj- := dummy.o
 
 # List of programs to build
-hostprogs-y := slabinfo page-types
+hostprogs-y := slabinfo page-types hugepage-mmap hugepage-shm map_hugetlb
 
 # Tell kbuild to always build the programs
 always := $(hostprogs-y)

trunk/Documentation/vm/hugepage-mmap.c

@@ -0,0 +1,91 @@
+/*
+ * hugepage-mmap:
+ *
+ * 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.
+ */
+
+#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)
+
+/* Only ia64 requires this */
+#ifdef __ia64__
+#define ADDR (void *)(0x8000000000000000UL)
+#define FLAGS (MAP_SHARED | MAP_FIXED)
+#else
+#define ADDR (void *)(0x0UL)
+#define FLAGS (MAP_SHARED)
+#endif
+
+static void check_bytes(char *addr)
+{
+	printf("First hex is %x\n", *((unsigned int *)addr));
+}
+
+static void write_bytes(char *addr)
+{
+	unsigned long i;
+
+	for (i = 0; i < LENGTH; i++)
+		*(addr + i) = (char)i;
+}
+
+static 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;
+}

trunk/Documentation/vm/hugepage-shm.c

@@ -0,0 +1,98 @@
+/*
+ * hugepage-shm:
+ *
+ * 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
+ */
+
+#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)
+
+/* Only ia64 requires this */
+#ifdef __ia64__
+#define ADDR (void *)(0x8000000000000000UL)
+#define SHMAT_FLAGS (SHM_RND)
+#else
+#define ADDR (void *)(0x0UL)
+#define SHMAT_FLAGS (0)
+#endif
+
+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;
+}