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Message-ID: <20070507193115.GA14264@dreamland.darkstar.lan>
Date: Mon, 7 May 2007 21:31:15 +0200
From: Luca Tettamanti <kronos.it@...il.com>
To: Andrea Righi <righiandr@...rs.sourceforge.net>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC][PATCH] VM: per-user overcommit policy
Hi,
a few comments on the patch:
Andrea Righi <righiandr@...rs.sourceforge.net> ha scritto:
> 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)
Ugly... very ugly ;)
Don't hide 'overcommit_memory' inside the ifdef block. The compiler
should be smart enough to optimize away the extra var.
There's also a problem with the #ifdef scattered all over the code. You
need a static inline 'vm_acct_get_config' for the !CONFIG_VM_ACCT_USER
case:
static inline int vm_acct_get_config(struct vm_acct_values *v,
uid_t uid)
{
return 0;
}
in this way you can remove the #ifdef. Futhermore, I'd also move the
branch with the fallback to sysctl values inside the vm_acct_get_config.
So, for !CONFIG_VM_ACCT_USER:
static inline int vm_acct_get_config(struct vm_acct_values *v,
uid_t uid)
{
v->overcommit_memory = sysctl_overcommit_memory;
v->overcommit_ratio = sysctl_overcommit_ratio;
}
(Yes, gcc will optimize it)
and for CONFIG_VM_ACCT_USER:
int vm_acct_get_config(struct vm_acct_values *v, uid_t uid)
{
if (found uid) {
v->overcommit_memory = foo;
v->overcommit_ratio = bar;
} else {
v->overcommit_memory = sysctl_overcommit_memory;
v->overcommit_ratio = sysctl_overcommit_ratio;
}
}
> 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:
In the error path (kzalloc failure) you release vm_acct_lock which is not
held.
> + 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;
^^ uh?
> +
> + /*
> + * 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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Luca
--
Porc i' mond che cio' sott i piedi!
V. Catozzo
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