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netfilter: iptables: lock free counters

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The reader/writer lock in ip_tables is acquired in the critical path of
processing packets and is one of the reasons just loading iptables can cause
a 20% performance loss. The rwlock serves two functions:

1) it prevents changes to table state (xt_replace) while table is in use.
   This is now handled by doing rcu on the xt_table. When table is
   replaced, the new table(s) are put in and the old one table(s) are freed
   after RCU period.

2) it provides synchronization when accesing the counter values.
   This is now handled by swapping in new table_info entries for each cpu
   then summing the old values, and putting the result back onto one
   cpu.  On a busy system it may cause sampling to occur at different
   times on each cpu, but no packet/byte counts are lost in the process.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

Sucessfully tested on my dual quad core machine too, but iptables only (no ipv6 here)
BTW, my new "tbench 8" result is 2450 MB/s, (it was 2150 MB/s not so long ago)

Acked-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Stephen Hemminger 2009-02-20 10:35:32 +01:00 committed by Patrick McHardy
parent 323dbf9638
commit 784544739a
5 changed files with 284 additions and 102 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/netfilter/x_tables.h
View File

@ -353,7 +353,7 @@ struct xt_table
unsigned int valid_hooks;
/* Lock for the curtain */
rwlock_t lock;
struct mutex lock;
/* Man behind the curtain... */
struct xt_table_info *private;
@ -385,7 +385,7 @@ struct xt_table_info
/* ipt_entry tables: one per CPU */
/* Note : this field MUST be the last one, see XT_TABLE_INFO_SZ */
char *entries[1];
void *entries[1];
};
#define XT_TABLE_INFO_SZ (offsetof(struct xt_table_info, entries) \
@ -432,6 +432,8 @@ extern void xt_proto_fini(struct net *net, u_int8_t af);
extern struct xt_table_info *xt_alloc_table_info(unsigned int size);
extern void xt_free_table_info(struct xt_table_info *info);
extern void xt_table_entry_swap_rcu(struct xt_table_info *old,
struct xt_table_info *new);
#ifdef CONFIG_COMPAT
#include <net/compat.h>

115
net/ipv4/netfilter/arp_tables.c
View File

@ -261,9 +261,10 @@ unsigned int arpt_do_table(struct sk_buff *skb,
indev = in ? in->name : nulldevname;
outdev = out ? out->name : nulldevname;
read_lock_bh(&table->lock);
private = table->private;
table_base = (void *)private->entries[smp_processor_id()];
rcu_read_lock();
private = rcu_dereference(table->private);
table_base = rcu_dereference(private->entries[smp_processor_id()]);
e = get_entry(table_base, private->hook_entry[hook]);
back = get_entry(table_base, private->underflow[hook]);
@ -335,7 +336,8 @@ unsigned int arpt_do_table(struct sk_buff *skb,
e = (void *)e + e->next_offset;
}
} while (!hotdrop);
read_unlock_bh(&table->lock);
rcu_read_unlock();
if (hotdrop)
return NF_DROP;
@ -738,11 +740,65 @@ static void get_counters(const struct xt_table_info *t,
}
}
static inline struct xt_counters *alloc_counters(struct xt_table *table)
/* We're lazy, and add to the first CPU; overflow works its fey magic
* and everything is OK. */
static int
add_counter_to_entry(struct arpt_entry *e,
const struct xt_counters addme[],
unsigned int *i)
{
ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
(*i)++;
return 0;
}
/* Take values from counters and add them back onto the current cpu */
static void put_counters(struct xt_table_info *t,
const struct xt_counters counters[])
{
unsigned int i, cpu;
local_bh_disable();
cpu = smp_processor_id();
i = 0;
ARPT_ENTRY_ITERATE(t->entries[cpu],
t->size,
add_counter_to_entry,
counters,
&i);
local_bh_enable();
}
static inline int
zero_entry_counter(struct arpt_entry *e, void *arg)
{
e->counters.bcnt = 0;
e->counters.pcnt = 0;
return 0;
}
static void
clone_counters(struct xt_table_info *newinfo, const struct xt_table_info *info)
{
unsigned int cpu;
const void *loc_cpu_entry = info->entries[raw_smp_processor_id()];
memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
for_each_possible_cpu(cpu) {
memcpy(newinfo->entries[cpu], loc_cpu_entry, info->size);
ARPT_ENTRY_ITERATE(newinfo->entries[cpu], newinfo->size,
zero_entry_counter, NULL);
}
}
static struct xt_counters *alloc_counters(struct xt_table *table)
{
unsigned int countersize;
struct xt_counters *counters;
const struct xt_table_info *private = table->private;
struct xt_table_info *private = table->private;
struct xt_table_info *info;
/* We need atomic snapshot of counters: rest doesn't change
* (other than comefrom, which userspace doesn't care
@ -752,14 +808,30 @@ static inline struct xt_counters *alloc_counters(struct xt_table *table)
counters = vmalloc_node(countersize, numa_node_id());
if (counters == NULL)
return ERR_PTR(-ENOMEM);
goto nomem;
/* First, sum counters... */
write_lock_bh(&table->lock);
get_counters(private, counters);
write_unlock_bh(&table->lock);
info = xt_alloc_table_info(private->size);
if (!info)
goto free_counters;
clone_counters(info, private);
mutex_lock(&table->lock);
xt_table_entry_swap_rcu(private, info);
synchronize_net(); /* Wait until smoke has cleared */
get_counters(info, counters);
put_counters(private, counters);
mutex_unlock(&table->lock);
xt_free_table_info(info);
return counters;
free_counters:
vfree(counters);
nomem:
return ERR_PTR(-ENOMEM);
}
static int copy_entries_to_user(unsigned int total_size,
@ -1099,20 +1171,6 @@ static int do_replace(struct net *net, void __user *user, unsigned int len)
return ret;
}
/* We're lazy, and add to the first CPU; overflow works its fey magic
* and everything is OK.
*/
static inline int add_counter_to_entry(struct arpt_entry *e,
const struct xt_counters addme[],
unsigned int *i)
{
ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
(*i)++;
return 0;
}
static int do_add_counters(struct net *net, void __user *user, unsigned int len,
int compat)
{
@ -1172,13 +1230,14 @@ static int do_add_counters(struct net *net, void __user *user, unsigned int len,
goto free;
}
write_lock_bh(&t->lock);
mutex_lock(&t->lock);
private = t->private;
if (private->number != num_counters) {
ret = -EINVAL;
goto unlock_up_free;
}
preempt_disable();
i = 0;
/* Choose the copy that is on our node */
loc_cpu_entry = private->entries[smp_processor_id()];
@ -1187,8 +1246,10 @@ static int do_add_counters(struct net *net, void __user *user, unsigned int len,
add_counter_to_entry,
paddc,
&i);
preempt_enable();
unlock_up_free:
write_unlock_bh(&t->lock);
mutex_unlock(&t->lock);
xt_table_unlock(t);
module_put(t->me);
free:

120
net/ipv4/netfilter/ip_tables.c
View File

@ -347,10 +347,12 @@ ipt_do_table(struct sk_buff *skb,
mtpar.family = tgpar.family = NFPROTO_IPV4;
tgpar.hooknum = hook;
read_lock_bh(&table->lock);
IP_NF_ASSERT(table->valid_hooks & (1 << hook));
private = table->private;
table_base = (void *)private->entries[smp_processor_id()];
rcu_read_lock();
private = rcu_dereference(table->private);
table_base = rcu_dereference(private->entries[smp_processor_id()]);
e = get_entry(table_base, private->hook_entry[hook]);
/* For return from builtin chain */
@ -445,7 +447,7 @@ ipt_do_table(struct sk_buff *skb,
}
} while (!hotdrop);
read_unlock_bh(&table->lock);
rcu_read_unlock();
#ifdef DEBUG_ALLOW_ALL
return NF_ACCEPT;
@ -924,13 +926,68 @@ get_counters(const struct xt_table_info *t,
counters,
&i);
}
}
/* We're lazy, and add to the first CPU; overflow works its fey magic
* and everything is OK. */
static int
add_counter_to_entry(struct ipt_entry *e,
const struct xt_counters addme[],
unsigned int *i)
{
ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
(*i)++;
return 0;
}
/* Take values from counters and add them back onto the current cpu */
static void put_counters(struct xt_table_info *t,
const struct xt_counters counters[])
{
unsigned int i, cpu;
local_bh_disable();
cpu = smp_processor_id();
i = 0;
IPT_ENTRY_ITERATE(t->entries[cpu],
t->size,
add_counter_to_entry,
counters,
&i);
local_bh_enable();
}
static inline int
zero_entry_counter(struct ipt_entry *e, void *arg)
{
e->counters.bcnt = 0;
e->counters.pcnt = 0;
return 0;
}
static void
clone_counters(struct xt_table_info *newinfo, const struct xt_table_info *info)
{
unsigned int cpu;
const void *loc_cpu_entry = info->entries[raw_smp_processor_id()];
memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
for_each_possible_cpu(cpu) {
memcpy(newinfo->entries[cpu], loc_cpu_entry, info->size);
IPT_ENTRY_ITERATE(newinfo->entries[cpu], newinfo->size,
zero_entry_counter, NULL);
}
}
static struct xt_counters * alloc_counters(struct xt_table *table)
{
unsigned int countersize;
struct xt_counters *counters;
const struct xt_table_info *private = table->private;
struct xt_table_info *private = table->private;
struct xt_table_info *info;
/* We need atomic snapshot of counters: rest doesn't change
(other than comefrom, which userspace doesn't care
@ -939,14 +996,30 @@ static struct xt_counters * alloc_counters(struct xt_table *table)
counters = vmalloc_node(countersize, numa_node_id());
if (counters == NULL)
return ERR_PTR(-ENOMEM);
goto nomem;
/* First, sum counters... */
write_lock_bh(&table->lock);
get_counters(private, counters);
write_unlock_bh(&table->lock);
info = xt_alloc_table_info(private->size);
if (!info)
goto free_counters;
clone_counters(info, private);
mutex_lock(&table->lock);
xt_table_entry_swap_rcu(private, info);
synchronize_net(); /* Wait until smoke has cleared */
get_counters(info, counters);
put_counters(private, counters);
mutex_unlock(&table->lock);
xt_free_table_info(info);
return counters;
free_counters:
vfree(counters);
nomem:
return ERR_PTR(-ENOMEM);
}
static int
@ -1312,27 +1385,6 @@ do_replace(struct net *net, void __user *user, unsigned int len)
return ret;
}
/* We're lazy, and add to the first CPU; overflow works its fey magic
* and everything is OK. */
static int
add_counter_to_entry(struct ipt_entry *e,
const struct xt_counters addme[],
unsigned int *i)
{
#if 0
duprintf("add_counter: Entry %u %lu/%lu + %lu/%lu\n",
*i,
(long unsigned int)e->counters.pcnt,
(long unsigned int)e->counters.bcnt,
(long unsigned int)addme[*i].pcnt,
(long unsigned int)addme[*i].bcnt);
#endif
ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
(*i)++;
return 0;
}
static int
do_add_counters(struct net *net, void __user *user, unsigned int len, int compat)
@ -1393,13 +1445,14 @@ do_add_counters(struct net *net, void __user *user, unsigned int len, int compat
goto free;
}
write_lock_bh(&t->lock);
mutex_lock(&t->lock);
private = t->private;
if (private->number != num_counters) {
ret = -EINVAL;
goto unlock_up_free;
}
preempt_disable();
i = 0;
/* Choose the copy that is on our node */
loc_cpu_entry = private->entries[raw_smp_processor_id()];
@ -1408,8 +1461,9 @@ do_add_counters(struct net *net, void __user *user, unsigned int len, int compat
add_counter_to_entry,
paddc,
&i);
preempt_enable();
unlock_up_free:
write_unlock_bh(&t->lock);
mutex_unlock(&t->lock);
xt_table_unlock(t);
module_put(t->me);
free:

119
net/ipv6/netfilter/ip6_tables.c
View File

@ -382,10 +382,12 @@ ip6t_do_table(struct sk_buff *skb,
mtpar.family = tgpar.family = NFPROTO_IPV6;
tgpar.hooknum = hook;
read_lock_bh(&table->lock);
IP_NF_ASSERT(table->valid_hooks & (1 << hook));
private = table->private;
table_base = (void *)private->entries[smp_processor_id()];
rcu_read_lock();
private = rcu_dereference(table->private);
table_base = rcu_dereference(private->entries[smp_processor_id()]);
e = get_entry(table_base, private->hook_entry[hook]);
/* For return from builtin chain */
@ -483,7 +485,7 @@ ip6t_do_table(struct sk_buff *skb,
#ifdef CONFIG_NETFILTER_DEBUG
((struct ip6t_entry *)table_base)->comefrom = NETFILTER_LINK_POISON;
#endif
read_unlock_bh(&table->lock);
rcu_read_unlock();
#ifdef DEBUG_ALLOW_ALL
return NF_ACCEPT;
@ -964,11 +966,64 @@ get_counters(const struct xt_table_info *t,
}
}
/* We're lazy, and add to the first CPU; overflow works its fey magic
* and everything is OK. */
static int
add_counter_to_entry(struct ip6t_entry *e,
const struct xt_counters addme[],
unsigned int *i)
{
ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
(*i)++;
return 0;
}
/* Take values from counters and add them back onto the current cpu */
static void put_counters(struct xt_table_info *t,
const struct xt_counters counters[])
{
unsigned int i, cpu;
local_bh_disable();
cpu = smp_processor_id();
i = 0;
IP6T_ENTRY_ITERATE(t->entries[cpu],
t->size,
add_counter_to_entry,
counters,
&i);
local_bh_enable();
}
static inline int
zero_entry_counter(struct ip6t_entry *e, void *arg)
{
e->counters.bcnt = 0;
e->counters.pcnt = 0;
return 0;
}
static void
clone_counters(struct xt_table_info *newinfo, const struct xt_table_info *info)
{
unsigned int cpu;
const void *loc_cpu_entry = info->entries[raw_smp_processor_id()];
memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
for_each_possible_cpu(cpu) {
memcpy(newinfo->entries[cpu], loc_cpu_entry, info->size);
IP6T_ENTRY_ITERATE(newinfo->entries[cpu], newinfo->size,
zero_entry_counter, NULL);
}
}
static struct xt_counters *alloc_counters(struct xt_table *table)
{
unsigned int countersize;
struct xt_counters *counters;
const struct xt_table_info *private = table->private;
struct xt_table_info *private = table->private;
struct xt_table_info *info;
/* We need atomic snapshot of counters: rest doesn't change
(other than comefrom, which userspace doesn't care
@ -977,14 +1032,28 @@ static struct xt_counters *alloc_counters(struct xt_table *table)
counters = vmalloc_node(countersize, numa_node_id());
if (counters == NULL)
return ERR_PTR(-ENOMEM);
goto nomem;
/* First, sum counters... */
write_lock_bh(&table->lock);
get_counters(private, counters);
write_unlock_bh(&table->lock);
info = xt_alloc_table_info(private->size);
if (!info)
goto free_counters;
return counters;
clone_counters(info, private);
mutex_lock(&table->lock);
xt_table_entry_swap_rcu(private, info);
synchronize_net(); /* Wait until smoke has cleared */
get_counters(info, counters);
put_counters(private, counters);
mutex_unlock(&table->lock);
xt_free_table_info(info);
free_counters:
vfree(counters);
nomem:
return ERR_PTR(-ENOMEM);
}
static int
@ -1351,28 +1420,6 @@ do_replace(struct net *net, void __user *user, unsigned int len)
return ret;
}
/* We're lazy, and add to the first CPU; overflow works its fey magic
* and everything is OK. */
static inline int
add_counter_to_entry(struct ip6t_entry *e,
const struct xt_counters addme[],
unsigned int *i)
{
#if 0
duprintf("add_counter: Entry %u %lu/%lu + %lu/%lu\n",
*i,
(long unsigned int)e->counters.pcnt,
(long unsigned int)e->counters.bcnt,
(long unsigned int)addme[*i].pcnt,
(long unsigned int)addme[*i].bcnt);
#endif
ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
(*i)++;
return 0;
}
static int
do_add_counters(struct net *net, void __user *user, unsigned int len,
int compat)
@ -1433,13 +1480,14 @@ do_add_counters(struct net *net, void __user *user, unsigned int len,
goto free;
}
write_lock_bh(&t->lock);
mutex_lock(&t->lock);
private = t->private;
if (private->number != num_counters) {
ret = -EINVAL;
goto unlock_up_free;
}
preempt_disable();
i = 0;
/* Choose the copy that is on our node */
loc_cpu_entry = private->entries[raw_smp_processor_id()];
@ -1448,8 +1496,9 @@ do_add_counters(struct net *net, void __user *user, unsigned int len,
add_counter_to_entry,
paddc,
&i);
preempt_enable();
unlock_up_free:
write_unlock_bh(&t->lock);
mutex_unlock(&t->lock);
xt_table_unlock(t);
module_put(t->me);
free:

26
net/netfilter/x_tables.c
View File

@ -625,6 +625,20 @@ void xt_free_table_info(struct xt_table_info *info)
}
EXPORT_SYMBOL(xt_free_table_info);
void xt_table_entry_swap_rcu(struct xt_table_info *oldinfo,
struct xt_table_info *newinfo)
{
unsigned int cpu;
for_each_possible_cpu(cpu) {
void *p = oldinfo->entries[cpu];
rcu_assign_pointer(oldinfo->entries[cpu], newinfo->entries[cpu]);
newinfo->entries[cpu] = p;
}
}
EXPORT_SYMBOL_GPL(xt_table_entry_swap_rcu);
/* Find table by name, grabs mutex & ref. Returns ERR_PTR() on error. */
struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
const char *name)
@ -671,21 +685,22 @@ xt_replace_table(struct xt_table *table,
struct xt_table_info *oldinfo, *private;
/* Do the substitution. */
write_lock_bh(&table->lock);
mutex_lock(&table->lock);
private = table->private;
/* Check inside lock: is the old number correct? */
if (num_counters != private->number) {
duprintf("num_counters != table->private->number (%u/%u)\n",
num_counters, private->number);
write_unlock_bh(&table->lock);
mutex_unlock(&table->lock);
*error = -EAGAIN;
return NULL;
}
oldinfo = private;
table->private = newinfo;
rcu_assign_pointer(table->private, newinfo);
newinfo->initial_entries = oldinfo->initial_entries;
write_unlock_bh(&table->lock);
mutex_unlock(&table->lock);
synchronize_net();
return oldinfo;
}
EXPORT_SYMBOL_GPL(xt_replace_table);
@ -719,7 +734,8 @@ struct xt_table *xt_register_table(struct net *net, struct xt_table *table,
/* Simplifies replace_table code. */
table->private = bootstrap;
rwlock_init(&table->lock);
mutex_init(&table->lock);
if (!xt_replace_table(table, 0, newinfo, &ret))
goto unlock;