[PATCH] MM: Support more pagesizes for MAP_HUGETLB/SHM_HUGETLB v7

From: Andi Kleen
Date: Mon Nov 05 2012 - 18:24:24 EST

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

There was some desire in large applications using MAP_HUGETLB/SHM_HUGETLB
to use 1GB huge pages on some mappings, and stay with 2MB on others. This
is useful together with NUMA policy: use 2MB interleaving on some mappings,
but 1GB on local mappings.

This patch extends the IPC/SHM syscall interfaces slightly to allow specifying
the page size.

It borrows some upper bits in the existing flag arguments and allows encoding
the log of the desired page size in addition to the *_HUGETLB flag.
When 0 is specified the default size is used, this makes the change fully
compatible.

Extending the internal hugetlb code to handle this is straight forward. Instead
of a single mount it just keeps an array of them and selects the right
mount based on the specified page size. When no page size is specified
it uses the mount of the default page size.

The change is not visible in /proc/mounts because internal mounts
don't appear there. It also has very little overhead: the additional
mounts just consume a super block, but not more memory when not used.

I also exported the new flags to the user headers
(they were previously under __KERNEL__). Right now only symbols
for x86 and some other architecture for 1GB and 2MB are defined.
The interface should already work for all other architectures
though. Only architectures that define multiple hugetlb sizes
actually need it (that is currently x86, tile, powerpc). However
tile and powerpc have user configurable hugetlb sizes, so it's
not easy to add defines. A program on those architectures would
need to query sysfs and use the appropiate log2.

v2: Port to new tree. Fix unmount.
v3: Ported to latest tree.
v4: Ported to latest tree. Minor changes for review feedback. Updated
description.
v5: Remove unnecessary prototypes to fix merge error (Hillf Danton)
v6: Rebased. Fix some unlikely error paths (Hillf Danton)
v7: Rebased.
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Hillf Danton <dhillf@xxxxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/mman.h | 3 ++
fs/hugetlbfs/inode.c | 66 ++++++++++++++++++++++++++++++--------
include/linux/hugetlb.h | 7 +++-
include/linux/shm.h | 19 +++++++++++
include/uapi/asm-generic/mman.h | 13 ++++++++
ipc/shm.c | 3 +-
mm/mmap.c | 5 ++-
7 files changed, 97 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/mman.h b/arch/x86/include/asm/mman.h
index 593e51d..513b05f 100644
--- a/arch/x86/include/asm/mman.h
+++ b/arch/x86/include/asm/mman.h
@@ -3,6 +3,9 @@

#define MAP_32BIT 0x40 /* only give out 32bit addresses */

+#define MAP_HUGE_2MB (21 << MAP_HUGE_SHIFT)
+#define MAP_HUGE_1GB (30 << MAP_HUGE_SHIFT)
+
#include <asm-generic/mman.h>

#endif /* _ASM_X86_MMAN_H */
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index c5bc355..f332275 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -923,7 +923,7 @@ static struct file_system_type hugetlbfs_fs_type = {
.kill_sb = kill_litter_super,
};

-static struct vfsmount *hugetlbfs_vfsmount;
+static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];

static int can_do_hugetlb_shm(void)
{
@@ -932,9 +932,22 @@ static int can_do_hugetlb_shm(void)
return capable(CAP_IPC_LOCK) || in_group_p(shm_group);
}

+static int get_hstate_idx(int page_size_log)
+{
+ struct hstate *h;
+
+ if (!page_size_log)
+ return default_hstate_idx;
+ h = size_to_hstate(1 << page_size_log);
+ if (!h)
+ return -1;
+ return h - hstates;
+}
+
struct file *hugetlb_file_setup(const char *name, unsigned long addr,
size_t size, vm_flags_t acctflag,
- struct user_struct **user, int creat_flags)
+ struct user_struct **user,
+ int creat_flags, int page_size_log)
{
int error = -ENOMEM;
struct file *file;
@@ -944,9 +957,14 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
struct qstr quick_string;
struct hstate *hstate;
unsigned long num_pages;
+ int hstate_idx;
+
+ hstate_idx = get_hstate_idx(page_size_log);
+ if (hstate_idx < 0)
+ return ERR_PTR(-ENODEV);

*user = NULL;
- if (!hugetlbfs_vfsmount)
+ if (!hugetlbfs_vfsmount[hstate_idx])
return ERR_PTR(-ENOENT);

if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
@@ -963,7 +981,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
}
}

- root = hugetlbfs_vfsmount->mnt_root;
+ root = hugetlbfs_vfsmount[hstate_idx]->mnt_root;
quick_string.name = name;
quick_string.len = strlen(quick_string.name);
quick_string.hash = 0;
@@ -971,7 +989,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
if (!path.dentry)
goto out_shm_unlock;

- path.mnt = mntget(hugetlbfs_vfsmount);
+ path.mnt = mntget(hugetlbfs_vfsmount[hstate_idx]);
error = -ENOSPC;
inode = hugetlbfs_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0);
if (!inode)
@@ -1011,8 +1029,9 @@ out_shm_unlock:

static int __init init_hugetlbfs_fs(void)
{
+ struct hstate *h;
int error;
- struct vfsmount *vfsmount;
+ int i;

error = bdi_init(&hugetlbfs_backing_dev_info);
if (error)
@@ -1029,14 +1048,27 @@ static int __init init_hugetlbfs_fs(void)
if (error)
goto out;

- vfsmount = kern_mount(&hugetlbfs_fs_type);
-
- if (!IS_ERR(vfsmount)) {
- hugetlbfs_vfsmount = vfsmount;
- return 0;
+ i = 0;
+ for_each_hstate (h) {
+ char buf[50];
+ unsigned ps_kb = 1U << (h->order + PAGE_SHIFT - 10);
+
+ snprintf(buf, sizeof buf, "pagesize=%uK", ps_kb);
+ hugetlbfs_vfsmount[i] = kern_mount_data(&hugetlbfs_fs_type,
+ buf);
+
+ if (IS_ERR(hugetlbfs_vfsmount[i])) {
+ pr_err(
+ "hugetlb: Cannot mount internal hugetlbfs for page size %uK",
+ ps_kb);
+ error = PTR_ERR(hugetlbfs_vfsmount[i]);
+ hugetlbfs_vfsmount[i] = NULL;
+ }
+ i++;
}
-
- error = PTR_ERR(vfsmount);
+ /* Non default hstates are optional */
+ if (!IS_ERR_OR_NULL(hugetlbfs_vfsmount[default_hstate_idx]))
+ return 0;

out:
kmem_cache_destroy(hugetlbfs_inode_cachep);
@@ -1047,13 +1079,19 @@ static int __init init_hugetlbfs_fs(void)

static void __exit exit_hugetlbfs_fs(void)
{
+ struct hstate *h;
+ int i;
+
+
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(hugetlbfs_inode_cachep);
- kern_unmount(hugetlbfs_vfsmount);
+ i = 0;
+ for_each_hstate (h)
+ kern_unmount(hugetlbfs_vfsmount[i++]);
unregister_filesystem(&hugetlbfs_fs_type);
bdi_destroy(&hugetlbfs_backing_dev_info);
}
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2251648..3e7fa1a 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -183,7 +183,8 @@ extern const struct file_operations hugetlbfs_file_operations;
extern const struct vm_operations_struct hugetlb_vm_ops;
struct file *hugetlb_file_setup(const char *name, unsigned long addr,
size_t size, vm_flags_t acct,
- struct user_struct **user, int creat_flags);
+ struct user_struct **user, int creat_flags,
+ int page_size_log);

static inline int is_file_hugepages(struct file *file)
{
@@ -195,12 +196,14 @@ static inline int is_file_hugepages(struct file *file)
return 0;
}

+
#else /* !CONFIG_HUGETLBFS */

#define is_file_hugepages(file) 0
static inline struct file *
hugetlb_file_setup(const char *name, unsigned long addr, size_t size,
- vm_flags_t acctflag, struct user_struct **user, int creat_flags)
+ vm_flags_t acctflag, struct user_struct **user, int creat_flags,
+ int page_size_log)
{
return ERR_PTR(-ENOSYS);
}
diff --git a/include/linux/shm.h b/include/linux/shm.h
index bcf8a6a..7bbab55 100644
--- a/include/linux/shm.h
+++ b/include/linux/shm.h
@@ -23,12 +23,31 @@ struct shmid_kernel /* private to the kernel */
struct task_struct *shm_creator;
};

+#endif
+
/* shm_mode upper byte flags */
#define SHM_DEST 01000 /* segment will be destroyed on last detach */
#define SHM_LOCKED 02000 /* segment will not be swapped */
#define SHM_HUGETLB 04000 /* segment will use huge TLB pages */
#define SHM_NORESERVE 010000 /* don't check for reservations */

+/* Bits [26:31] are reserved */
+
+/*
+ * When SHM_HUGETLB is set bits [26:31] encode the log2 of the huge page size.
+ * This gives us 6 bits, which is enough until someone invents 128 bit address
+ * spaces.
+ *
+ * Assume these are all power of twos.
+ * When 0 use the default page size.
+ */
+#define SHM_HUGE_SHIFT 26
+#define SHM_HUGE_MASK 0x3f
+#define SHM_HUGE_2MB (21 << SHM_HUGE_SHIFT)
+#define SHM_HUGE_1GB (30 << SHM_HUGE_SHIFT)
+
+#ifdef __KERNEL__
+
#ifdef CONFIG_SYSVIPC
long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr,
unsigned long shmlba);
diff --git a/include/uapi/asm-generic/mman.h b/include/uapi/asm-generic/mman.h
index 32c8bd6..d2f35d8 100644
--- a/include/uapi/asm-generic/mman.h
+++ b/include/uapi/asm-generic/mman.h
@@ -13,6 +13,19 @@
#define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x40000 /* create a huge page mapping */

+/* Bits [26:31] are reserved */
+
+/*
+ * When MAP_HUGETLB is set bits [26:31] encode the log2 of the huge page size.
+ * This gives us 6 bits, which is enough until someone invents 128 bit address
+ * spaces.
+ *
+ * Assume these are all power of twos.
+ * When 0 use the default page size.
+ */
+#define MAP_HUGE_SHIFT 26
+#define MAP_HUGE_MASK 0x3f
+
#define MCL_CURRENT 1 /* lock all current mappings */
#define MCL_FUTURE 2 /* lock all future mappings */

diff --git a/ipc/shm.c b/ipc/shm.c
index dff40c9..4fa6d8f 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -495,7 +495,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
if (shmflg & SHM_NORESERVE)
acctflag = VM_NORESERVE;
file = hugetlb_file_setup(name, 0, size, acctflag,
- &shp->mlock_user, HUGETLB_SHMFS_INODE);
+ &shp->mlock_user, HUGETLB_SHMFS_INODE,
+ (shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);
} else {
/*
* Do not allow no accounting for OVERCOMMIT_NEVER, even
diff --git a/mm/mmap.c b/mm/mmap.c
index 2d94235..04e990b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1151,8 +1151,9 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
* memory so no accounting is necessary
*/
file = hugetlb_file_setup(HUGETLB_ANON_FILE, addr, len,
- VM_NORESERVE, &user,
- HUGETLB_ANONHUGE_INODE);
+ VM_NORESERVE,
+ &user, HUGETLB_ANONHUGE_INODE,
+ (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
if (IS_ERR(file))
return PTR_ERR(file);
}
--
1.7.7.6

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