The patch titled
hugetlb: add MAP_HUGETLB example
has been added to the -mm tree. Its filename is
hugetlb-add-map_hugetlb-example.patch
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out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: hugetlb: add MAP_HUGETLB example
From: Eric B Munson <ebmunson@xxxxxxxxxx>
Add an example of how to use the MAP_HUGETLB flag to the vm documentation
directory and a reference to the example in hugetlbpage.txt.
Signed-off-by: Eric B Munson <ebmunson@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Adam Litke <agl@xxxxxxxxxx>
Cc: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/00-INDEX | 2
Documentation/vm/hugetlbpage.txt | 14 +++--
Documentation/vm/map_hugetlb.c | 77 +++++++++++++++++++++++++++++
3 files changed, 87 insertions(+), 6 deletions(-)
diff -puN Documentation/vm/00-INDEX~hugetlb-add-map_hugetlb-example Documentation/vm/00-INDEX
--- a/Documentation/vm/00-INDEX~hugetlb-add-map_hugetlb-example
+++ a/Documentation/vm/00-INDEX
@@ -22,3 +22,5 @@ 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.
diff -puN Documentation/vm/hugetlbpage.txt~hugetlb-add-map_hugetlb-example Documentation/vm/hugetlbpage.txt
--- a/Documentation/vm/hugetlbpage.txt~hugetlb-add-map_hugetlb-example
+++ a/Documentation/vm/hugetlbpage.txt
@@ -187,12 +187,14 @@ Regular chown, chgrp, and chmod commands
used to change the file attributes on hugetlbfs.
Also, it is important to note that no such mount command is required if the
-applications are going to use only shmat/shmget system calls. Users who
-wish to use hugetlb page via shared memory segment should be a member of
-a supplementary group and system admin needs to configure that gid into
-/proc/sys/vm/hugetlb_shm_group. It is possible for same or different
-applications to use any combination of mmaps and shm* calls, though the
-mount of filesystem will be required for using mmap calls.
+applications are going to use only shmat/shmget system calls or mmap with
+MAP_HUGETLB. Users who wish to use hugetlb page via shared memory segment
+should be a member of a supplementary group and system admin needs to
+configure that gid into /proc/sys/vm/hugetlb_shm_group. It is possible for
+same or different applications to use any combination of mmaps and shm*
+calls, though the mount of filesystem will be required for using mmap calls
+without MAP_HUGETLB. For an example of how to use mmap with MAP_HUGETLB see
+map_hugetlb.c.
*******************************************************************
diff -puN /dev/null Documentation/vm/map_hugetlb.c
--- /dev/null
+++ a/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;
+}
_
Patches currently in -mm which might be from ebmunson@xxxxxxxxxx are
hugetlbfs-allow-the-creation-of-files-suitable-for-map_private-on-the-vfs-internal-mount.patch
hugetlb-add-map_hugetlb-for-mmaping-pseudo-anonymous-huge-page-regions.patch
hugetlb-add-map_hugetlb-example.patch
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