| Message ID | 20090413095309.631cf395@nehalam |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
Stephen Hemminger a écrit : > This is an alternative version of ip/ip6/arp tables locking using > per-cpu locks. This avoids the overhead of synchronize_net() during > update but still removes the expensive rwlock in earlier versions. > > The idea for this came from an earlier version done by Eric Duzamet. > Locking is done per-cpu, the fast path locks on the current cpu > and updates counters. The slow case involves acquiring the locks on > all cpu's. > > The mutex that was added for 2.6.30 in xt_table is unnecessary since > there already is a mutex for xt[af].mutex that is held. > > Tested basic functionality (add/remove/list), but don't have test cases > for stress, ip6tables or arptables. > > Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Patch seems good to me, but apparently xt_replace_table() misses the "acquiring the locks on all cpus" you mentioned in ChangeLog ? I am still off-computers until tomorrow so cannot provide a patch for this, sorry. Some form of local_bh_disable(); for_each_possible_cpu(cpu) spin_lock(&per_cpu(ip_tables_lock, cpu)); oldinfo = private; /* do the substitution */ table->private = newinfo; newinfo->initial_entries = oldinfo->initial_entries; for_each_possible_cpu(cpu) spin_unlock(&per_cpu(ip_tables_lock, cpu)); local_bh_enable(); But I wonder if this could hit a limit of max spinlocks held by this cpu, say on a 4096 cpu machine ? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 13 Apr 2009 19:40:24 +0200 Eric Dumazet <dada1@cosmosbay.com> wrote: > Stephen Hemminger a écrit : > > This is an alternative version of ip/ip6/arp tables locking using > > per-cpu locks. This avoids the overhead of synchronize_net() during > > update but still removes the expensive rwlock in earlier versions. > > > > The idea for this came from an earlier version done by Eric Duzamet. > > Locking is done per-cpu, the fast path locks on the current cpu > > and updates counters. The slow case involves acquiring the locks on > > all cpu's. > > > > The mutex that was added for 2.6.30 in xt_table is unnecessary since > > there already is a mutex for xt[af].mutex that is held. > > > > Tested basic functionality (add/remove/list), but don't have test cases > > for stress, ip6tables or arptables. > > > > Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> > > Patch seems good to me, but apparently xt_replace_table() > misses the "acquiring the locks on all cpus" you mentioned in ChangeLog ? It happens in get_counters already. > I am still off-computers until tomorrow so cannot provide a patch for this, sorry. > > Some form of > > local_bh_disable(); > for_each_possible_cpu(cpu) > spin_lock(&per_cpu(ip_tables_lock, cpu)); > > oldinfo = private; > /* do the substitution */ > table->private = newinfo; > newinfo->initial_entries = oldinfo->initial_entries; > > for_each_possible_cpu(cpu) > spin_unlock(&per_cpu(ip_tables_lock, cpu)); > local_bh_enable(); > > > But I wonder if this could hit a limit of max spinlocks held by this cpu, say on a 4096 cpu machine ? > > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 13 Apr 2009, Stephen Hemminger wrote: > This is an alternative version of ip/ip6/arp tables locking using > per-cpu locks. This avoids the overhead of synchronize_net() during > update but still removes the expensive rwlock in earlier versions. > > The idea for this came from an earlier version done by Eric Duzamet. > Locking is done per-cpu, the fast path locks on the current cpu > and updates counters. The slow case involves acquiring the locks on > all cpu's. Doesn't spin_lock() result in a pipeline flush on x86? iirc there was a benchmark in an RCU paper that tested using per cpu spin_locks and the result was that it didn't scale well at all. /Martin -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 13 Apr 2009, Martin Josefsson wrote: > > Doesn't spin_lock() result in a pipeline flush on x86? It's about 20-40 cycles when cached and uncontended, with some outliers (50+ cycles on P4, 12 cycles on some AMD opterons). So it's not a big deal if you actually hit that case. > iirc there was a benchmark in an RCU paper that tested using per cpu > spin_locks and the result was that it didn't scale well at all. Spinlocks scale wonderfully well if you only touch them on one CPU. Of course, if you truly only touch them on one CPU they are pointless, but a "all normal code only touches the local CPU spinlock, the really odd cases take all locks" approach works fine. It makes the uncommon case really quite slow, but if it truly is uncommon, that's fine. Linus -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 13 Apr 2009 09:53:09 -0700 Stephen Hemminger <shemminger@vyatta.com> wrote: > This is an alternative version of ip/ip6/arp tables locking using > per-cpu locks. This avoids the overhead of synchronize_net() during > update but still removes the expensive rwlock in earlier versions. > > The idea for this came from an earlier version done by Eric Duzamet. > Locking is done per-cpu, the fast path locks on the current cpu > and updates counters. The slow case involves acquiring the locks on > all cpu's. > > The mutex that was added for 2.6.30 in xt_table is unnecessary since > there already is a mutex for xt[af].mutex that is held. > > Tested basic functionality (add/remove/list), but don't have test cases > for stress, ip6tables or arptables. > > unsigned int > ipt_do_table(struct sk_buff *skb, > @@ -339,9 +341,10 @@ ipt_do_table(struct sk_buff *skb, > > IP_NF_ASSERT(table->valid_hooks & (1 << hook)); > > - rcu_read_lock_bh(); > - private = rcu_dereference(table->private); > - table_base = rcu_dereference(private->entries[smp_processor_id()]); > + local_bh_disable(); > + spin_lock(&__get_cpu_var(ip_tables_lock)); spin_lock_bh()? > + private = table->private; > + table_base = private->entries[smp_processor_id()]; > > e = get_entry(table_base, private->hook_entry[hook]); > > @@ -436,8 +439,8 @@ ipt_do_table(struct sk_buff *skb, > e = (void *)e + e->next_offset; > } > } while (!hotdrop); > - > - rcu_read_unlock_bh(); > + spin_unlock(&__get_cpu_var(ip_tables_lock)); > + local_bh_enable(); > > #ifdef DEBUG_ALLOW_ALL > return NF_ACCEPT; > @@ -891,86 +894,34 @@ get_counters(const struct xt_table_info > struct xt_counters counters[]) > { > unsigned int cpu; > - unsigned int i; > - unsigned int curcpu; > + unsigned int i = 0; > + unsigned int curcpu = raw_smp_processor_id(); > > /* Instead of clearing (by a previous call to memset()) > * the counters and using adds, we set the counters > * with data used by 'current' CPU > * We dont care about preemption here. > */ > - curcpu = raw_smp_processor_id(); > - > - i = 0; > + spin_lock_bh(&per_cpu(ip_tables_lock, curcpu)); > IPT_ENTRY_ITERATE(t->entries[curcpu], > t->size, > set_entry_to_counter, > counters, > &i); > + spin_unlock_bh(&per_cpu(ip_tables_lock, curcpu)); > > for_each_possible_cpu(cpu) { > if (cpu == curcpu) > continue; > + > i = 0; > + spin_lock_bh(&per_cpu(ip_tables_lock, cpu)); > IPT_ENTRY_ITERATE(t->entries[cpu], > t->size, > add_entry_to_counter, > counters, > &i); > - } This would be racy against cpu hotplug if this code was hotplug-aware. And it should be hotplug aware, really. num_possible_cpus() can exceed num_online_cpus(). The extent by which possible>online is controversial, but one can conceive of situations where it is "lots". Is lib/percpu_counter.c no good for this application? Unfixably no good? That code automagically handles cpu hotplug. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 13 Apr 2009 15:24:37 -0700 Andrew Morton <akpm@linux-foundation.org> wrote: > On Mon, 13 Apr 2009 09:53:09 -0700 > Stephen Hemminger <shemminger@vyatta.com> wrote: > > > This is an alternative version of ip/ip6/arp tables locking using > > per-cpu locks. This avoids the overhead of synchronize_net() during > > update but still removes the expensive rwlock in earlier versions. > > > > The idea for this came from an earlier version done by Eric Duzamet. > > Locking is done per-cpu, the fast path locks on the current cpu > > and updates counters. The slow case involves acquiring the locks on > > all cpu's. > > > > The mutex that was added for 2.6.30 in xt_table is unnecessary since > > there already is a mutex for xt[af].mutex that is held. > > > > Tested basic functionality (add/remove/list), but don't have test cases > > for stress, ip6tables or arptables. > > > > unsigned int > > ipt_do_table(struct sk_buff *skb, > > @@ -339,9 +341,10 @@ ipt_do_table(struct sk_buff *skb, > > > > IP_NF_ASSERT(table->valid_hooks & (1 << hook)); > > > > - rcu_read_lock_bh(); > > - private = rcu_dereference(table->private); > > - table_base = rcu_dereference(private->entries[smp_processor_id()]); > > + local_bh_disable(); > > + spin_lock(&__get_cpu_var(ip_tables_lock)); > > spin_lock_bh()? No. get_cpu_var implies smp_processor_id which is not safe without preempt_disable (ie bh disable). > > > + private = table->private; > > + table_base = private->entries[smp_processor_id()]; > > > > e = get_entry(table_base, private->hook_entry[hook]); > > > > @@ -436,8 +439,8 @@ ipt_do_table(struct sk_buff *skb, > > e = (void *)e + e->next_offset; > > } > > } while (!hotdrop); > > - > > - rcu_read_unlock_bh(); > > + spin_unlock(&__get_cpu_var(ip_tables_lock)); > > + local_bh_enable(); > > > > #ifdef DEBUG_ALLOW_ALL > > return NF_ACCEPT; > > @@ -891,86 +894,34 @@ get_counters(const struct xt_table_info > > struct xt_counters counters[]) > > { > > unsigned int cpu; > > - unsigned int i; > > - unsigned int curcpu; > > + unsigned int i = 0; > > + unsigned int curcpu = raw_smp_processor_id(); > > > > /* Instead of clearing (by a previous call to memset()) > > * the counters and using adds, we set the counters > > * with data used by 'current' CPU > > * We dont care about preemption here. > > */ > > - curcpu = raw_smp_processor_id(); > > - > > - i = 0; > > + spin_lock_bh(&per_cpu(ip_tables_lock, curcpu)); > > IPT_ENTRY_ITERATE(t->entries[curcpu], > > t->size, > > set_entry_to_counter, > > counters, > > &i); > > + spin_unlock_bh(&per_cpu(ip_tables_lock, curcpu)); > > > > for_each_possible_cpu(cpu) { > > if (cpu == curcpu) > > continue; > > + > > i = 0; > > + spin_lock_bh(&per_cpu(ip_tables_lock, cpu)); > > IPT_ENTRY_ITERATE(t->entries[cpu], > > t->size, > > add_entry_to_counter, > > counters, > > &i); > > - } > > This would be racy against cpu hotplug if this code was hotplug-aware. > > And it should be hotplug aware, really. num_possible_cpus() can exceed > num_online_cpus(). The extent by which possible>online is > controversial, but one can conceive of situations where it is "lots". It is doing right thing already with hotplug. This code still needs to count packets processed by previously online cpu, that is no longer there. > Is lib/percpu_counter.c no good for this application? Unfixably no > good? That code automagically handles cpu hotplug. percpu_counter can't deal with the layout/load here. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 13 Apr 2009 16:20:00 -0700 Stephen Hemminger <shemminger@vyatta.com> wrote: > On Mon, 13 Apr 2009 15:24:37 -0700 > Andrew Morton <akpm@linux-foundation.org> wrote: > > > On Mon, 13 Apr 2009 09:53:09 -0700 > > Stephen Hemminger <shemminger@vyatta.com> wrote: > > > > > This is an alternative version of ip/ip6/arp tables locking using > > > per-cpu locks. This avoids the overhead of synchronize_net() during > > > update but still removes the expensive rwlock in earlier versions. > > > > > > The idea for this came from an earlier version done by Eric Duzamet. > > > Locking is done per-cpu, the fast path locks on the current cpu > > > and updates counters. The slow case involves acquiring the locks on > > > all cpu's. > > > > > > The mutex that was added for 2.6.30 in xt_table is unnecessary since > > > there already is a mutex for xt[af].mutex that is held. > > > > > > Tested basic functionality (add/remove/list), but don't have test cases > > > for stress, ip6tables or arptables. > > > > > > unsigned int > > > ipt_do_table(struct sk_buff *skb, > > > @@ -339,9 +341,10 @@ ipt_do_table(struct sk_buff *skb, > > > > > > IP_NF_ASSERT(table->valid_hooks & (1 << hook)); > > > > > > - rcu_read_lock_bh(); > > > - private = rcu_dereference(table->private); > > > - table_base = rcu_dereference(private->entries[smp_processor_id()]); > > > + local_bh_disable(); > > > + spin_lock(&__get_cpu_var(ip_tables_lock)); > > > > spin_lock_bh()? > > No. get_cpu_var implies smp_processor_id which is not safe > without preempt_disable (ie bh disable). spin_lock_bh() will dtrt, but spelling it out seems a good idea. It should have an explanatory comment, IMO. > > > > And it should be hotplug aware, really. num_possible_cpus() can exceed > > num_online_cpus(). The extent by which possible>online is > > controversial, but one can conceive of situations where it is "lots". > > It is doing right thing already with hotplug. It's slow. > This code still needs to count packets processed by previously online > cpu, that is no longer there. Those counts could be migrated off that CPU when it is offlined. As percpucounter does. > > Is lib/percpu_counter.c no good for this application? Unfixably no > > good? That code automagically handles cpu hotplug. > > percpu_counter can't deal with the layout/load here. Insufficient detail here for anyone to understand why percpucounter cannot be adapted to this requirement. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 13 Apr 2009, Andrew Morton wrote: > > > > > > > > - rcu_read_lock_bh(); > > > > - private = rcu_dereference(table->private); > > > > - table_base = rcu_dereference(private->entries[smp_processor_id()]); > > > > + local_bh_disable(); > > > > + spin_lock(&__get_cpu_var(ip_tables_lock)); > > > > > > spin_lock_bh()? > > > > No. get_cpu_var implies smp_processor_id which is not safe > > without preempt_disable (ie bh disable). > > spin_lock_bh() will dtrt, but spelling it out seems a good idea. No, spin_lock_bh() will _not_ do the right thing. On UP it will actually work for two reasons: it will work because (a) it's UP, so there are no issues with smp_processor_id() to beging with, but also because even if there _were_ issues, it would still work because it would all expand as a macro, and the preempt_disable() will actually happen before the argument is evaluated. But on SMP, spin_lock_bh() expands to just _spin_lock_bh(), and is a real function - and the argument will be evaluated before the call (obviously), and thus before the preempt_disable(). So local_bh_disable(); spin_lock(&__get_cpu_var(ip_tables_lock)); is correct, and spin_lock_bh(&__get_cpu_var(ip_tables_lock)); is _not_ correct. The latter will do "&__get_cpu_var(ip_tables_lock)" with no protection from the process being switched to another CPU. Linus -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
* Linus Torvalds <torvalds@linux-foundation.org> wrote: > > > On Mon, 13 Apr 2009, Andrew Morton wrote: > > > > > > > > > > - rcu_read_lock_bh(); > > > > > - private = rcu_dereference(table->private); > > > > > - table_base = rcu_dereference(private->entries[smp_processor_id()]); > > > > > + local_bh_disable(); > > > > > + spin_lock(&__get_cpu_var(ip_tables_lock)); > > > > > > > > spin_lock_bh()? > > > > > > No. get_cpu_var implies smp_processor_id which is not safe > > > without preempt_disable (ie bh disable). > > > > spin_lock_bh() will dtrt, but spelling it out seems a good idea. > > No, spin_lock_bh() will _not_ do the right thing. > > On UP it will actually work for two reasons: it will work because (a) it's > UP, so there are no issues with smp_processor_id() to beging with, but > also because even if there _were_ issues, it would still work because it > would all expand as a macro, and the preempt_disable() will actually > happen before the argument is evaluated. > > But on SMP, spin_lock_bh() expands to just _spin_lock_bh(), and is > a real function - and the argument will be evaluated before the > call (obviously), and thus before the preempt_disable(). > > So > > local_bh_disable(); > spin_lock(&__get_cpu_var(ip_tables_lock)); > > is correct, and > > spin_lock_bh(&__get_cpu_var(ip_tables_lock)); > > is _not_ correct. The latter will do > "&__get_cpu_var(ip_tables_lock)" with no protection from the > process being switched to another CPU. One option would be to make it more robust for such use. The downside would be all the other cases where the expression is really constant (but still takes a few instructions to calculate) and could be (and should be) evaluated outside of that critical section. So i'd tend to leave it in its current (optimistic) form: we've got 1283 uses of spin_lock_bh(), and just a quick look at git grep suggests that the current optimistic optimization matters in practice. Ingo -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Stephen Hemminger wrote: > This is an alternative version of ip/ip6/arp tables locking using > per-cpu locks. This avoids the overhead of synchronize_net() during > update but still removes the expensive rwlock in earlier versions. > > The idea for this came from an earlier version done by Eric Duzamet. > Locking is done per-cpu, the fast path locks on the current cpu > and updates counters. The slow case involves acquiring the locks on > all cpu's. > > The mutex that was added for 2.6.30 in xt_table is unnecessary since > there already is a mutex for xt[af].mutex that is held. > > Tested basic functionality (add/remove/list), but don't have test cases > for stress, ip6tables or arptables. Thanks Stephen, I'll do some testing with ip6tables. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/include/linux/netfilter/x_tables.h 2009-04-13 08:27:45.698412446 -0700 +++ b/include/linux/netfilter/x_tables.h 2009-04-13 08:34:05.499348295 -0700 @@ -354,9 +354,6 @@ struct xt_table /* What hooks you will enter on */ unsigned int valid_hooks; - /* Lock for the curtain */ - struct mutex lock; - /* Man behind the curtain... */ struct xt_table_info *private; @@ -434,8 +431,6 @@ extern void xt_proto_fini(struct net *ne 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); /* * This helper is performance critical and must be inlined --- a/net/ipv4/netfilter/ip_tables.c 2009-04-13 08:27:45.684411824 -0700 +++ b/net/ipv4/netfilter/ip_tables.c 2009-04-13 09:12:54.295536361 -0700 @@ -297,6 +297,8 @@ static void trace_packet(struct sk_buff } #endif +static DEFINE_PER_CPU(spinlock_t, ip_tables_lock); + /* Returns one of the generic firewall policies, like NF_ACCEPT. */ unsigned int ipt_do_table(struct sk_buff *skb, @@ -339,9 +341,10 @@ ipt_do_table(struct sk_buff *skb, IP_NF_ASSERT(table->valid_hooks & (1 << hook)); - rcu_read_lock_bh(); - private = rcu_dereference(table->private); - table_base = rcu_dereference(private->entries[smp_processor_id()]); + local_bh_disable(); + spin_lock(&__get_cpu_var(ip_tables_lock)); + private = table->private; + table_base = private->entries[smp_processor_id()]; e = get_entry(table_base, private->hook_entry[hook]); @@ -436,8 +439,8 @@ ipt_do_table(struct sk_buff *skb, e = (void *)e + e->next_offset; } } while (!hotdrop); - - rcu_read_unlock_bh(); + spin_unlock(&__get_cpu_var(ip_tables_lock)); + local_bh_enable(); #ifdef DEBUG_ALLOW_ALL return NF_ACCEPT; @@ -891,86 +894,34 @@ get_counters(const struct xt_table_info struct xt_counters counters[]) { unsigned int cpu; - unsigned int i; - unsigned int curcpu; + unsigned int i = 0; + unsigned int curcpu = raw_smp_processor_id(); /* Instead of clearing (by a previous call to memset()) * the counters and using adds, we set the counters * with data used by 'current' CPU * We dont care about preemption here. */ - curcpu = raw_smp_processor_id(); - - i = 0; + spin_lock_bh(&per_cpu(ip_tables_lock, curcpu)); IPT_ENTRY_ITERATE(t->entries[curcpu], t->size, set_entry_to_counter, counters, &i); + spin_unlock_bh(&per_cpu(ip_tables_lock, curcpu)); for_each_possible_cpu(cpu) { if (cpu == curcpu) continue; + i = 0; + spin_lock_bh(&per_cpu(ip_tables_lock, cpu)); IPT_ENTRY_ITERATE(t->entries[cpu], t->size, add_entry_to_counter, 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); + spin_unlock_bh(&per_cpu(ip_tables_lock, cpu)); } } @@ -979,7 +930,6 @@ static struct xt_counters * alloc_counte unsigned int countersize; struct xt_counters *counters; 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 @@ -990,26 +940,10 @@ static struct xt_counters * alloc_counte if (counters == NULL) goto nomem; - 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); + get_counters(private, counters); return counters; - free_counters: - vfree(counters); nomem: return ERR_PTR(-ENOMEM); } @@ -1377,6 +1311,18 @@ do_replace(struct net *net, void __user 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) +{ + 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) @@ -1386,7 +1332,7 @@ do_add_counters(struct net *net, void __ struct xt_counters *paddc; unsigned int num_counters; const char *name; - int size; + int curcpu, size; void *ptmp; struct xt_table *t; const struct xt_table_info *private; @@ -1437,25 +1383,27 @@ do_add_counters(struct net *net, void __ goto free; } - mutex_lock(&t->lock); private = t->private; if (private->number != num_counters) { ret = -EINVAL; goto unlock_up_free; } - preempt_disable(); i = 0; + local_bh_disable(); /* Choose the copy that is on our node */ - loc_cpu_entry = private->entries[raw_smp_processor_id()]; + curcpu = smp_processor_id(); + spin_lock(&__get_cpu_var(ip_tables_lock)); + loc_cpu_entry = private->entries[curcpu]; IPT_ENTRY_ITERATE(loc_cpu_entry, private->size, add_counter_to_entry, paddc, &i); - preempt_enable(); + spin_unlock(&__get_cpu_var(ip_tables_lock)); + local_bh_enable(); + unlock_up_free: - mutex_unlock(&t->lock); xt_table_unlock(t); module_put(t->me); free: @@ -2272,7 +2220,10 @@ static struct pernet_operations ip_table static int __init ip_tables_init(void) { - int ret; + int cpu, ret; + + for_each_possible_cpu(cpu) + spin_lock_init(&per_cpu(ip_tables_lock, cpu)); ret = register_pernet_subsys(&ip_tables_net_ops); if (ret < 0) --- a/net/netfilter/x_tables.c 2009-04-13 08:27:45.671412509 -0700 +++ b/net/netfilter/x_tables.c 2009-04-13 09:19:51.687537585 -0700 @@ -625,20 +625,6 @@ void xt_free_table_info(struct xt_table_ } 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) @@ -685,22 +671,18 @@ xt_replace_table(struct xt_table *table, struct xt_table_info *oldinfo, *private; /* Do the substitution. */ - 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); - mutex_unlock(&table->lock); *error = -EAGAIN; return NULL; } oldinfo = private; - rcu_assign_pointer(table->private, newinfo); + table->private = newinfo; newinfo->initial_entries = oldinfo->initial_entries; - mutex_unlock(&table->lock); - synchronize_net(); return oldinfo; } EXPORT_SYMBOL_GPL(xt_replace_table); @@ -734,7 +716,6 @@ struct xt_table *xt_register_table(struc /* Simplifies replace_table code. */ table->private = bootstrap; - mutex_init(&table->lock); if (!xt_replace_table(table, 0, newinfo, &ret)) goto unlock; --- a/net/ipv6/netfilter/ip6_tables.c 2009-04-13 08:37:58.189723514 -0700 +++ b/net/ipv6/netfilter/ip6_tables.c 2009-04-13 09:14:26.576349680 -0700 @@ -329,6 +329,8 @@ static void trace_packet(struct sk_buff } #endif +static DEFINE_PER_CPU(spinlock_t, ip6_tables_lock); + /* Returns one of the generic firewall policies, like NF_ACCEPT. */ unsigned int ip6t_do_table(struct sk_buff *skb, @@ -365,9 +367,10 @@ ip6t_do_table(struct sk_buff *skb, IP_NF_ASSERT(table->valid_hooks & (1 << hook)); - rcu_read_lock_bh(); - private = rcu_dereference(table->private); - table_base = rcu_dereference(private->entries[smp_processor_id()]); + local_bh_disable(); + spin_lock(&__get_cpu_var(ip6_tables_lock)); + private = table->private; + table_base = private->entries[smp_processor_id()]; e = get_entry(table_base, private->hook_entry[hook]); @@ -466,7 +469,8 @@ ip6t_do_table(struct sk_buff *skb, #ifdef CONFIG_NETFILTER_DEBUG ((struct ip6t_entry *)table_base)->comefrom = NETFILTER_LINK_POISON; #endif - rcu_read_unlock_bh(); + spin_unlock(&__get_cpu_var(ip6_tables_lock)); + local_bh_enable(); #ifdef DEBUG_ALLOW_ALL return NF_ACCEPT; @@ -920,84 +924,33 @@ get_counters(const struct xt_table_info struct xt_counters counters[]) { unsigned int cpu; - unsigned int i; - unsigned int curcpu; + unsigned int i = 0; + unsigned int curcpu = raw_smp_processor_id(); /* Instead of clearing (by a previous call to memset()) * the counters and using adds, we set the counters * with data used by 'current' CPU * We dont care about preemption here. */ - curcpu = raw_smp_processor_id(); - - i = 0; + spin_lock_bh(&per_cpu(ip6_tables_lock, curcpu)); IP6T_ENTRY_ITERATE(t->entries[curcpu], t->size, set_entry_to_counter, counters, &i); + spin_unlock_bh(&per_cpu(ip6_tables_lock, curcpu)); for_each_possible_cpu(cpu) { if (cpu == curcpu) continue; i = 0; + spin_lock_bh(&per_cpu(ip6_tables_lock, cpu)); IP6T_ENTRY_ITERATE(t->entries[cpu], t->size, add_entry_to_counter, 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 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); + spin_unlock_bh(&per_cpu(ip6_tables_lock, cpu)); } } @@ -1006,7 +959,6 @@ static struct xt_counters *alloc_counter unsigned int countersize; struct xt_counters *counters; 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 @@ -1017,26 +969,9 @@ static struct xt_counters *alloc_counter if (counters == NULL) goto nomem; - 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); - + get_counters(private, counters); return counters; - free_counters: - vfree(counters); nomem: return ERR_PTR(-ENOMEM); } @@ -1405,6 +1340,19 @@ do_replace(struct net *net, void __user 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 ip6t_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) @@ -1414,7 +1362,7 @@ do_add_counters(struct net *net, void __ struct xt_counters *paddc; unsigned int num_counters; char *name; - int size; + int curcpu, size; void *ptmp; struct xt_table *t; const struct xt_table_info *private; @@ -1465,25 +1413,27 @@ do_add_counters(struct net *net, void __ goto free; } - mutex_lock(&t->lock); private = t->private; if (private->number != num_counters) { ret = -EINVAL; goto unlock_up_free; } - preempt_disable(); i = 0; + local_bh_disable(); /* Choose the copy that is on our node */ - loc_cpu_entry = private->entries[raw_smp_processor_id()]; + curcpu = smp_processor_id(); + spin_lock(&__get_cpu_var(ip6_tables_lock)); + loc_cpu_entry = private->entries[curcpu]; IP6T_ENTRY_ITERATE(loc_cpu_entry, private->size, add_counter_to_entry, paddc, &i); - preempt_enable(); + spin_unlock(&__get_cpu_var(ip6_tables_lock)); + local_bh_enable(); + unlock_up_free: - mutex_unlock(&t->lock); xt_table_unlock(t); module_put(t->me); free: @@ -2298,7 +2248,10 @@ static struct pernet_operations ip6_tabl static int __init ip6_tables_init(void) { - int ret; + int cpu, ret; + + for_each_possible_cpu(cpu) + spin_lock_init(&per_cpu(ip6_tables_lock, cpu)); ret = register_pernet_subsys(&ip6_tables_net_ops); if (ret < 0) --- a/net/ipv4/netfilter/arp_tables.c 2009-04-13 08:38:05.803598692 -0700 +++ b/net/ipv4/netfilter/arp_tables.c 2009-04-13 09:19:57.079411426 -0700 @@ -231,6 +231,8 @@ static inline struct arpt_entry *get_ent return (struct arpt_entry *)(base + offset); } +static DEFINE_PER_CPU(spinlock_t, arp_tables_lock); + unsigned int arpt_do_table(struct sk_buff *skb, unsigned int hook, const struct net_device *in, @@ -253,9 +255,10 @@ unsigned int arpt_do_table(struct sk_buf indev = in ? in->name : nulldevname; outdev = out ? out->name : nulldevname; - rcu_read_lock_bh(); - private = rcu_dereference(table->private); - table_base = rcu_dereference(private->entries[smp_processor_id()]); + local_bh_disable(); + spin_lock(&__get_cpu_var(arp_tables_lock)); + private = table->private; + table_base = private->entries[smp_processor_id()]; e = get_entry(table_base, private->hook_entry[hook]); back = get_entry(table_base, private->underflow[hook]); @@ -328,8 +331,8 @@ unsigned int arpt_do_table(struct sk_buf e = (void *)e + e->next_offset; } } while (!hotdrop); - - rcu_read_unlock_bh(); + spin_unlock(&__get_cpu_var(arp_tables_lock)); + local_bh_enable(); if (hotdrop) return NF_DROP; @@ -705,85 +708,33 @@ static void get_counters(const struct xt struct xt_counters counters[]) { unsigned int cpu; - unsigned int i; - unsigned int curcpu; + unsigned int i = 0; + unsigned int curcpu = raw_smp_processor_id(); /* Instead of clearing (by a previous call to memset()) * the counters and using adds, we set the counters * with data used by 'current' CPU * We dont care about preemption here. */ - curcpu = raw_smp_processor_id(); - - i = 0; + spin_lock_bh(&per_cpu(arp_tables_lock, curcpu)); ARPT_ENTRY_ITERATE(t->entries[curcpu], t->size, set_entry_to_counter, counters, &i); + spin_unlock_bh(&per_cpu(arp_tables_lock, curcpu)); for_each_possible_cpu(cpu) { if (cpu == curcpu) continue; i = 0; + spin_lock_bh(&per_cpu(arp_tables_lock, cpu)); ARPT_ENTRY_ITERATE(t->entries[cpu], t->size, add_entry_to_counter, 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 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); + spin_unlock_bh(&per_cpu(arp_tables_lock, cpu)); } } @@ -792,7 +743,6 @@ static struct xt_counters *alloc_counter unsigned int countersize; struct xt_counters *counters; 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 @@ -804,26 +754,10 @@ static struct xt_counters *alloc_counter if (counters == NULL) goto nomem; - 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); + get_counters(private, counters); return counters; - free_counters: - vfree(counters); nomem: return ERR_PTR(-ENOMEM); } @@ -1165,6 +1099,19 @@ static int do_replace(struct net *net, v 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 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) { @@ -1173,7 +1120,7 @@ static int do_add_counters(struct net *n struct xt_counters *paddc; unsigned int num_counters; const char *name; - int size; + int curcpu, size; void *ptmp; struct xt_table *t; const struct xt_table_info *private; @@ -1224,25 +1171,26 @@ static int do_add_counters(struct net *n goto free; } - 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()]; + local_bh_disable(); + curcpu = smp_processor_id(); + spin_lock(&__get_cpu_var(arp_tables_lock)); + loc_cpu_entry = private->entries[curcpu]; ARPT_ENTRY_ITERATE(loc_cpu_entry, private->size, add_counter_to_entry, paddc, &i); - preempt_enable(); + spin_unlock(&__get_cpu_var(arp_tables_lock)); + local_bh_enable(); unlock_up_free: - mutex_unlock(&t->lock); xt_table_unlock(t); module_put(t->me);
This is an alternative version of ip/ip6/arp tables locking using per-cpu locks. This avoids the overhead of synchronize_net() during update but still removes the expensive rwlock in earlier versions. The idea for this came from an earlier version done by Eric Duzamet. Locking is done per-cpu, the fast path locks on the current cpu and updates counters. The slow case involves acquiring the locks on all cpu's. The mutex that was added for 2.6.30 in xt_table is unnecessary since there already is a mutex for xt[af].mutex that is held. Tested basic functionality (add/remove/list), but don't have test cases for stress, ip6tables or arptables. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> --- Patch against 2.6.30-rc1 include/linux/netfilter/x_tables.h | 5 - net/ipv4/netfilter/arp_tables.c | 122 ++++++++++------------------------ net/ipv4/netfilter/ip_tables.c | 129 +++++++++++-------------------------- net/ipv6/netfilter/ip6_tables.c | 127 +++++++++++------------------------- net/netfilter/x_tables.c | 21 ------ 5 files changed, 116 insertions(+), 288 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html