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Subject[RFC][PATCH] VM: per-user overcommit policy
Date
Allow to define per-UID virtual memory overcommit handling. Configuration is
stored in a hash list in kernel space reachable through /proc/overcommit_uid
(surely there're better ways to do it, i.e. via configfs).

Hash elements are defined using a triple:

uid:overcommit_memory:overcommit_ratio

The overcommit_* values have the same semantic of their respective sysctl
variables.

If a user is not present in the hash, the default system policy will be used
(defined by /proc/sys/vm/overcommit_memory and /proc/sys/vm/overcommit_ratio).

Example:

- Enable "always overcommit" policy for admin:
root@host # echo 0:1:0 > /proc/overcommit_uid
- processes belonging to sshd (uid=100) and ntp (uid=102) users can be quite
critical, so use a classic heuristic overcommit:
root@host # echo 100:0:50 > /proc/overcommit_uid
root@host # echo 102:0:50 > /proc/overcommit_uid
- allow uid=1001 and uid=1002 (common users) to allocate memory only if the
total committed space is below the 50% of the physical RAM + the size of
swap:
root@host # echo 1001:2:50 > /proc/overcommit_uid
root@host # echo 1002:2:50 > /proc/overcommit_uid
- Deny VM allocation to others:
root@host # echo 2 > /proc/sys/vm/overcommit_memory && echo 0 > /proc/sys/vm/overcommit_ratio
TODO:
- GID overcommit policy,
- per-user/group VM accounting,
- VM quotas,
- a lot of improvements,
- more testing...

Signed-off-by: Andrea Righi <a.righi@cineca.it>
---
diff -urpN linux-2.6.21/include/linux/mman.h linux-2.6.21-vm-acct-user/include/linux/mman.h
--- linux-2.6.21/include/linux/mman.h 2007-05-07 20:20:24.000000000 +0200
+++ linux-2.6.21-vm-acct-user/include/linux/mman.h 2007-05-07 20:20:42.000000000 +0200
@@ -18,6 +18,14 @@
extern int sysctl_overcommit_memory;
extern int sysctl_overcommit_ratio;
extern atomic_t vm_committed_space;
+#ifdef CONFIG_VM_ACCT_USER
+struct vm_acct_values
+{
+ int overcommit_memory;
+ int overcommit_ratio;
+};
+extern int vm_acct_get_config(struct vm_acct_values *v, uid_t uid);
+#endif

#ifdef CONFIG_SMP
extern void vm_acct_memory(long pages);
diff -urpN linux-2.6.21/ipc/shm.c linux-2.6.21-vm-acct-user/ipc/shm.c
--- linux-2.6.21/ipc/shm.c 2007-05-07 20:20:24.000000000 +0200
+++ linux-2.6.21-vm-acct-user/ipc/shm.c 2007-05-07 20:20:42.000000000 +0200
@@ -370,12 +370,24 @@ static int newseg (struct ipc_namespace
shp->mlock_user = current->user;
} else {
int acctflag = VM_ACCOUNT;
+#ifdef CONFIG_VM_ACCT_USER
+ int overcommit_memory;
+ struct vm_acct_values v;
+
+ if (!vm_acct_get_config(&v, current->uid)) {
+ overcommit_memory = v.overcommit_memory;
+ } else {
+ overcommit_memory = sysctl_overcommit_memory;
+ }
+#else
+#define overcommit_memory sysctl_overcommit_memory
+#endif
/*
* Do not allow no accounting for OVERCOMMIT_NEVER, even
* if it's asked for.
*/
if ((shmflg & SHM_NORESERVE) &&
- sysctl_overcommit_memory != OVERCOMMIT_NEVER)
+ overcommit_memory != OVERCOMMIT_NEVER)
acctflag = 0;
sprintf (name, "SYSV%08x", key);
file = shmem_file_setup(name, size, acctflag);
diff -urpN linux-2.6.21/mm/Kconfig linux-2.6.21-vm-acct-user/mm/Kconfig
--- linux-2.6.21/mm/Kconfig 2007-05-07 20:20:24.000000000 +0200
+++ linux-2.6.21-vm-acct-user/mm/Kconfig 2007-05-07 20:21:21.000000000 +0200
@@ -163,3 +163,11 @@ config ZONE_DMA_FLAG
default "0" if !ZONE_DMA
default "1"

+config VM_ACCT_USER
+ bool "Per-user VM overcommit policy (EXPERIMENTAL)"
+ depends on PROC_FS && EXPERIMENTAL
+ def_bool n
+ help
+ Say Y here to enable per-user virtual memory overcommit handling.
+ Overcommit configuration will be available via /proc/overcommit_uid.
+
diff -urpN linux-2.6.21/mm/mmap.c linux-2.6.21-vm-acct-user/mm/mmap.c
--- linux-2.6.21/mm/mmap.c 2007-05-07 20:20:24.000000000 +0200
+++ linux-2.6.21-vm-acct-user/mm/mmap.c 2007-05-07 20:20:42.000000000 +0200
@@ -95,16 +95,30 @@ atomic_t vm_committed_space = ATOMIC_INI
int __vm_enough_memory(long pages, int cap_sys_admin)
{
unsigned long free, allowed;
-
+#ifdef CONFIG_VM_ACCT_USER
+ int overcommit_memory, overcommit_ratio;
+ struct vm_acct_values v;
+
+ if (!vm_acct_get_config(&v, current->uid)) {
+ overcommit_memory = v.overcommit_memory;
+ overcommit_ratio = v.overcommit_ratio;
+ } else {
+ overcommit_memory = sysctl_overcommit_memory;
+ overcommit_ratio = sysctl_overcommit_ratio;
+ }
+#else
+#define overcommit_memory sysctl_overcommit_memory
+#define overcommit_ratio sysctl_overcommit_ratio
+#endif
vm_acct_memory(pages);

/*
* Sometimes we want to use more memory than we have
*/
- if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
+ if (overcommit_memory == OVERCOMMIT_ALWAYS)
return 0;

- if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
+ if (overcommit_memory == OVERCOMMIT_GUESS) {
unsigned long n;

free = global_page_state(NR_FILE_PAGES);
@@ -155,7 +169,7 @@ int __vm_enough_memory(long pages, int c
}

allowed = (totalram_pages - hugetlb_total_pages())
- * sysctl_overcommit_ratio / 100;
+ * overcommit_ratio / 100;
/*
* Leave the last 3% for root
*/
@@ -901,6 +915,10 @@ unsigned long do_mmap_pgoff(struct file
struct rb_node ** rb_link, * rb_parent;
int accountable = 1;
unsigned long charged = 0, reqprot = prot;
+#ifdef CONFIG_VM_ACCT_USER
+ int overcommit_memory;
+ struct vm_acct_values v;
+#endif

/*
* Does the application expect PROT_READ to imply PROT_EXEC?
@@ -1040,8 +1058,15 @@ munmap_back:
if (!may_expand_vm(mm, len >> PAGE_SHIFT))
return -ENOMEM;

+#ifdef CONFIG_VM_ACCT_USER
+ if (!vm_acct_get_config(&v, current->uid)) {
+ overcommit_memory = v.overcommit_memory;
+ } else {
+ overcommit_memory = sysctl_overcommit_memory;
+ }
+#endif
if (accountable && (!(flags & MAP_NORESERVE) ||
- sysctl_overcommit_memory == OVERCOMMIT_NEVER)) {
+ overcommit_memory == OVERCOMMIT_NEVER)) {
if (vm_flags & VM_SHARED) {
/* Check memory availability in shmem_file_setup? */
vm_flags |= VM_ACCOUNT;
diff -urpN linux-2.6.21/mm/nommu.c linux-2.6.21-vm-acct-user/mm/nommu.c
--- linux-2.6.21/mm/nommu.c 2007-05-07 20:20:24.000000000 +0200
+++ linux-2.6.21-vm-acct-user/mm/nommu.c 2007-05-07 20:20:42.000000000 +0200
@@ -1240,16 +1240,31 @@ EXPORT_SYMBOL(get_unmapped_area);
int __vm_enough_memory(long pages, int cap_sys_admin)
{
unsigned long free, allowed;
+#ifdef CONFIG_VM_ACCT_USER
+ int overcommit_memory, overcommit_ratio;
+ struct vm_acct_values v;
+
+ if (!vm_acct_get_config(&v, current->uid)) {
+ overcommit_memory = v.overcommit_memory;
+ overcommit_ratio = v.overcommit_ratio;
+ } else {
+ overcommit_memory = sysctl_overcommit_memory;
+ overcommit_ratio = sysctl_overcommit_ratio;
+ }
+#else
+#define overcommit_memory sysctl_overcommit_memory
+#define overcommit_ratio sysctl_overcommit_ratio
+#endif

vm_acct_memory(pages);

/*
* Sometimes we want to use more memory than we have
*/
- if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
+ if (overcommit_memory == OVERCOMMIT_ALWAYS)
return 0;

- if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
+ if (overcommit_memory == OVERCOMMIT_GUESS) {
unsigned long n;

free = global_page_state(NR_FILE_PAGES);
@@ -1299,7 +1314,7 @@ int __vm_enough_memory(long pages, int c
goto error;
}

- allowed = totalram_pages * sysctl_overcommit_ratio / 100;
+ allowed = totalram_pages * overcommit_ratio / 100;
/*
* Leave the last 3% for root
*/
diff -urpN linux-2.6.21/mm/swap.c linux-2.6.21-vm-acct-user/mm/swap.c
--- linux-2.6.21/mm/swap.c 2007-05-07 20:20:24.000000000 +0200
+++ linux-2.6.21-vm-acct-user/mm/swap.c 2007-05-07 20:20:42.000000000 +0200
@@ -30,6 +30,10 @@
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/init.h>
+#include <linux/hash.h>
+#include <linux/seq_file.h>
+#include <linux/kernel.h>
+#include <linux/proc_fs.h>

/* How many pages do we try to swap or page in/out together? */
int page_cluster;
@@ -455,6 +459,196 @@ unsigned pagevec_lookup_tag(struct pagev

EXPORT_SYMBOL(pagevec_lookup_tag);

+#ifdef CONFIG_VM_ACCT_USER
+
+#define VM_ACCT_HASH_SHIFT 10
+#define VM_ACCT_HASH_SIZE (1UL << VM_ACCT_HASH_SHIFT)
+#define vm_acct_hashfn(uid) hash_long((unsigned long)uid, VM_ACCT_HASH_SHIFT)
+
+/* User VM overcommit configuration */
+typedef struct vm_acct_hash_struct
+{
+ uid_t uid;
+ struct vm_acct_values val;
+ struct hlist_node vm_acct_chain;
+} vm_acct_hash_t;
+
+/* Hash list used to store per-user VM overcommit configurations */
+static struct hlist_head *vm_acct_hash;
+
+/* VM overcommit hash table spinlock */
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(vm_acct_lock);
+
+/*
+ * Get user VM configuration from the hash list.
+ */
+int vm_acct_get_config(struct vm_acct_values *v, uid_t uid)
+{
+ struct hlist_node *elem;
+ vm_acct_hash_t *p;
+
+ spin_lock_irq(&vm_acct_lock);
+ hlist_for_each_entry(p, elem, &vm_acct_hash[vm_acct_hashfn(uid)],
+ vm_acct_chain) {
+ if (p->uid == uid) {
+ v->overcommit_memory = p->val.overcommit_memory;
+ v->overcommit_ratio = p->val.overcommit_ratio;
+ spin_unlock_irq(&vm_acct_lock);
+ return 0;
+ }
+ }
+ spin_unlock_irq(&vm_acct_lock);
+
+ return -ENOENT;
+}
+
+/*
+ * Create a new element in the VM configuration hash list.
+ */
+static int __vm_acct_set_element(uid_t uid,
+ int overcommit_memory, int overcommit_ratio)
+{
+ struct hlist_node *elem;
+ vm_acct_hash_t *p;
+ int ret = 0;
+
+ spin_lock_irq(&vm_acct_lock);
+ hlist_for_each_entry(p, elem, &vm_acct_hash[vm_acct_hashfn(uid)],
+ vm_acct_chain) {
+ if (p->uid == uid) {
+ p->val.overcommit_memory = overcommit_memory;
+ p->val.overcommit_ratio = overcommit_ratio;
+ goto out;
+ }
+ }
+ spin_unlock_irq(&vm_acct_lock);
+
+ /* Allocate new element */
+ p = kzalloc(sizeof(*p), GFP_KERNEL);
+ if (unlikely(!p)) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ p->uid = uid;
+ p->val.overcommit_memory = overcommit_memory;
+ p->val.overcommit_ratio = overcommit_ratio;
+
+ spin_lock_irq(&vm_acct_lock);
+ hlist_add_head(&p->vm_acct_chain, &vm_acct_hash[vm_acct_hashfn(uid)]);
+out:
+ spin_unlock_irq(&vm_acct_lock);
+ return ret;
+}
+
+/*
+ * Set VM user parameters via /proc/overcommit_uid.
+ */
+static int vm_acct_set(struct file *filp, const char __user *buffer,
+ size_t count, loff_t *data)
+{
+ char buf[128];
+ char *om, *or;
+ int __ret;
+
+ /*
+ * Parse ':'-separated arguments
+ * uid:overcommit_memory:overcommit_ratio
+ */
+ if (count > sizeof(buf) - 1)
+ return -EFAULT;
+
+ if (copy_from_user(buf, buffer, count))
+ return -EFAULT;
+
+ buf[sizeof(buf) - 1] = '\0';
+
+ om = strstr(buf, ":");
+ if ((om == NULL) || (*++om == '\0')) {
+ return -EINVAL;
+ }
+
+ or = strstr(om, ":");
+ if ((or == NULL) || (*++or == '\0')) {
+ return -EINVAL;
+ }
+
+ /* Set VM configuration */
+ __ret = __vm_acct_set_element((uid_t)simple_strtoul(buf, NULL, 10),
+ (int)simple_strtol(om, NULL, 10),
+ (int)simple_strtol(or, NULL, 10));
+ if (__ret)
+ return __ret;
+
+ return count;
+}
+
+/*
+ * Print VM overcommit configurations.
+ */
+static int vm_acct_show(struct seq_file *m, void *v)
+{
+ struct hlist_node *elem;
+ vm_acct_hash_t *p;
+ int i;
+
+ spin_lock_irq(&vm_acct_lock);
+ for (i = 0; i < VM_ACCT_HASH_SIZE; i++) {
+ if (!&vm_acct_hash[i])
+ continue;
+ hlist_for_each_entry(p, elem, &vm_acct_hash[i],
+ vm_acct_chain) {
+ seq_printf(m, "%i:%i:%i\n",
+ p->uid, p->val.overcommit_memory,
+ p->val.overcommit_ratio);
+ }
+ }
+ spin_unlock_irq(&vm_acct_lock);
+
+ return 0;
+}
+
+static int vm_acct_open(struct inode *inode, struct file *filp)
+{
+ return single_open(filp, vm_acct_show, NULL);
+}
+
+static struct file_operations vm_acct_ops = {
+ .open = vm_acct_open,
+ .read = seq_read,
+ .write = vm_acct_set,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static int __init init_vm_acct(void)
+{
+ struct proc_dir_entry *pe;
+ int i;
+
+ vm_acct_hash = kmalloc(VM_ACCT_HASH_SIZE * sizeof(*(vm_acct_hash)),
+ GFP_KERNEL);
+ if (!vm_acct_hash)
+ return -ENOMEM;
+
+ printk(KERN_INFO "vm_acct_uid hash table entries: %lu\n",
+ VM_ACCT_HASH_SIZE / sizeof(*(vm_acct_hash)));
+
+ spin_lock_irq(&vm_acct_lock);
+ for (i = 0; i < VM_ACCT_HASH_SIZE; i++)
+ INIT_HLIST_HEAD(&vm_acct_hash[i]);
+ spin_unlock_irq(&vm_acct_lock);
+
+ pe = create_proc_entry("overcommit_uid", 0600, NULL);
+ if (!pe)
+ return -ENOMEM;
+ pe->proc_fops = &vm_acct_ops;
+
+ return 0;
+}
+__initcall(init_vm_acct);
+
+#endif /* CONFIG_VM_ACCT_USER */
+
#ifdef CONFIG_SMP
/*
* We tolerate a little inaccuracy to avoid ping-ponging the counter between
-
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