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netfilter: x_tables: dont block BH while reading counters

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Using "iptables -L" with a lot of rules have a too big BH latency.
Jesper mentioned ~6 ms and worried of frame drops.

Switch to a per_cpu seqlock scheme, so that taking a snapshot of
counters doesnt need to block BH (for this cpu, but also other cpus).

This adds two increments on seqlock sequence per ipt_do_table() call,
its a reasonable cost for allowing "iptables -L" not block BH
processing.

Reported-by: Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Eric Dumazet
2011-01-10 20:11:38 +01:00
committed by Pablo Neira Ayuso
parent 45b9f509b7
commit 83723d6071
5 changed files with 49 additions and 99 deletions
Download Patch File Download Diff File Expand all files Collapse all files

45
net/ipv4/netfilter/arp_tables.c
View File

@@ -710,42 +710,25 @@ static void get_counters(const struct xt_table_info *t,
struct arpt_entry *iter;
unsigned int cpu;
unsigned int i;
unsigned int curcpu = get_cpu();
/* Instead of clearing (by a previous call to memset())
* the counters and using adds, we set the counters
* with data used by 'current' CPU
*
* Bottom half has to be disabled to prevent deadlock
* if new softirq were to run and call ipt_do_table
*/
local_bh_disable();
i = 0;
xt_entry_foreach(iter, t->entries[curcpu], t->size) {
SET_COUNTER(counters[i], iter->counters.bcnt,
iter->counters.pcnt);
++i;
}
local_bh_enable();
/* Processing counters from other cpus, we can let bottom half enabled,
* (preemption is disabled)
*/
for_each_possible_cpu(cpu) {
if (cpu == curcpu)
continue;
seqlock_t *lock = &per_cpu(xt_info_locks, cpu).lock;
i = 0;
local_bh_disable();
xt_info_wrlock(cpu);
xt_entry_foreach(iter, t->entries[cpu], t->size) {
ADD_COUNTER(counters[i], iter->counters.bcnt,
iter->counters.pcnt);
u64 bcnt, pcnt;
unsigned int start;
do {
start = read_seqbegin(lock);
bcnt = iter->counters.bcnt;
pcnt = iter->counters.pcnt;
} while (read_seqretry(lock, start));
ADD_COUNTER(counters[i], bcnt, pcnt);
++i;
}
xt_info_wrunlock(cpu);
local_bh_enable();
}
put_cpu();
}
static struct xt_counters *alloc_counters(const struct xt_table *table)
@@ -759,7 +742,7 @@ static struct xt_counters *alloc_counters(const struct xt_table *table)
* about).
*/
countersize = sizeof(struct xt_counters) * private->number;
counters = vmalloc(countersize);
counters = vzalloc(countersize);
if (counters == NULL)
return ERR_PTR(-ENOMEM);
@@ -1007,7 +990,7 @@ static int __do_replace(struct net *net, const char *name,
struct arpt_entry *iter;
ret = 0;
counters = vmalloc(num_counters * sizeof(struct xt_counters));
counters = vzalloc(num_counters * sizeof(struct xt_counters));
if (!counters) {
ret = -ENOMEM;
goto out;

45
net/ipv4/netfilter/ip_tables.c
View File

@@ -884,42 +884,25 @@ get_counters(const struct xt_table_info *t,
struct ipt_entry *iter;
unsigned int cpu;
unsigned int i;
unsigned int curcpu = get_cpu();
/* Instead of clearing (by a previous call to memset())
* the counters and using adds, we set the counters
* with data used by 'current' CPU.
*
* Bottom half has to be disabled to prevent deadlock
* if new softirq were to run and call ipt_do_table
*/
local_bh_disable();
i = 0;
xt_entry_foreach(iter, t->entries[curcpu], t->size) {
SET_COUNTER(counters[i], iter->counters.bcnt,
iter->counters.pcnt);
++i;
}
local_bh_enable();
/* Processing counters from other cpus, we can let bottom half enabled,
* (preemption is disabled)
*/
for_each_possible_cpu(cpu) {
if (cpu == curcpu)
continue;
seqlock_t *lock = &per_cpu(xt_info_locks, cpu).lock;
i = 0;
local_bh_disable();
xt_info_wrlock(cpu);
xt_entry_foreach(iter, t->entries[cpu], t->size) {
ADD_COUNTER(counters[i], iter->counters.bcnt,
iter->counters.pcnt);
u64 bcnt, pcnt;
unsigned int start;
do {
start = read_seqbegin(lock);
bcnt = iter->counters.bcnt;
pcnt = iter->counters.pcnt;
} while (read_seqretry(lock, start));
ADD_COUNTER(counters[i], bcnt, pcnt);
++i; /* macro does multi eval of i */
}
xt_info_wrunlock(cpu);
local_bh_enable();
}
put_cpu();
}
static struct xt_counters *alloc_counters(const struct xt_table *table)
@@ -932,7 +915,7 @@ static struct xt_counters *alloc_counters(const struct xt_table *table)
(other than comefrom, which userspace doesn't care
about). */
countersize = sizeof(struct xt_counters) * private->number;
counters = vmalloc(countersize);
counters = vzalloc(countersize);
if (counters == NULL)
return ERR_PTR(-ENOMEM);
@@ -1203,7 +1186,7 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
struct ipt_entry *iter;
ret = 0;
counters = vmalloc(num_counters * sizeof(struct xt_counters));
counters = vzalloc(num_counters * sizeof(struct xt_counters));
if (!counters) {
ret = -ENOMEM;
goto out;