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Date: Fri, 28 Feb 2014 10:47:38 +0100
From: Jesper Dangaard Brouer <brouer@...hat.com>
To: David Miller <davem@...emloft.net>
Cc: netfilter-devel@...r.kernel.org, eric.dumazet@...il.com,
pablo@...filter.org, netdev@...r.kernel.org, fw@...len.de,
kaber@...sh.net
Subject: Re: [nf-next PATCH 0/5] (repost) netfilter: conntrack:
optimization, remove central spinlock
On Thu, 27 Feb 2014 18:34:15 -0500 (EST)
David Miller <davem@...emloft.net> wrote:
> From: Jesper Dangaard Brouer <brouer@...hat.com>
> Date: Thu, 27 Feb 2014 19:23:24 +0100
>
> > (Repost to netfilter-devel list)
> >
> > This patchset change the conntrack locking and provides a huge
> > performance improvements.
> >
> > This patchset is based upon Eric Dumazet's proposed patch:
> > http://thread.gmane.org/gmane.linux.network/268758/focus=47306
> > I have in agreement with Eric Dumazet, taken over this patch (and
> > turned it into a entire patchset).
> >
> > Primary focus is to remove the central spinlock nf_conntrack_lock.
> > This requires several steps to be acheived.
>
> I only worry about the raw_smp_processor_id()'s.
>
> If preemption will be disabled in these contexts, then it's safe and
> we can just use plain smp_processor_id().
Most of the contexts are safe, one were not by mistake, and one is not.
I've corrected the code (patch diff below) and tested with lockdep etc.
> If preemption is not necessarily disabled in these spots, the use
> is not correct. We'll need to use get_cpu/put_cpu sequences, or
> (considering what these patches are doing) something like:
>
> struct ct_pcpu *pcpu;
>
> /* add this conntrack to the (per cpu) unconfirmed list */
> local_bh_disable();
> ct->cpu = smp_processor_id();
> pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);
>
> spin_lock(&pcpu->lock);
> hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
> &pcpu->unconfirmed);
> spin_unlock_bh(&pcpu->lock);
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Sr. Network Kernel Developer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index ac85fd1..289b279 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -192,34 +192,37 @@ clean_from_lists(struct nf_conn *ct)
nf_ct_remove_expectations(ct);
}
+/* must be called with local_bh_disable */
static void nf_ct_add_to_dying_list(struct nf_conn *ct)
{
struct ct_pcpu *pcpu;
/* add this conntrack to the (per cpu) dying list */
- ct->cpu = raw_smp_processor_id();
+ ct->cpu = smp_processor_id();
pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);
- spin_lock_bh(&pcpu->lock);
+ spin_lock(&pcpu->lock);
hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
&pcpu->dying);
- spin_unlock_bh(&pcpu->lock);
+ spin_unlock(&pcpu->lock);
}
+/* must be called with local_bh_disable */
static void nf_ct_add_to_unconfirmed_list(struct nf_conn *ct)
{
struct ct_pcpu *pcpu;
/* add this conntrack to the (per cpu) unconfirmed list */
- ct->cpu = raw_smp_processor_id();
+ ct->cpu = smp_processor_id();
pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);
- spin_lock_bh(&pcpu->lock);
+ spin_lock(&pcpu->lock);
hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
&pcpu->unconfirmed);
- spin_unlock_bh(&pcpu->lock);
+ spin_unlock(&pcpu->lock);
}
+/* must be called with local_bh_disable */
static void nf_ct_del_from_dying_or_unconfirmed_list(struct nf_conn *ct)
{
struct ct_pcpu *pcpu;
@@ -227,10 +230,10 @@ static void nf_ct_del_from_dying_or_unconfirmed_list(struct nf_conn *ct)
/* We overload first tuple to link into unconfirmed or dying list.*/
pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);
- spin_lock_bh(&pcpu->lock);
+ spin_lock(&pcpu->lock);
BUG_ON(hlist_nulls_unhashed(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode));
hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
- spin_unlock_bh(&pcpu->lock);
+ spin_unlock(&pcpu->lock);
}
static void
@@ -511,10 +514,11 @@ void nf_conntrack_tmpl_insert(struct net *net, struct nf_conn *tmpl)
nf_conntrack_get(&tmpl->ct_general);
/* add this conntrack to the (per cpu) tmpl list */
- tmpl->cpu = raw_smp_processor_id();
+ local_bh_disable();
+ tmpl->cpu = smp_processor_id();
pcpu = per_cpu_ptr(nf_ct_net(tmpl)->ct.pcpu_lists, tmpl->cpu);
- spin_lock_bh(&pcpu->lock);
+ spin_lock(&pcpu->lock);
/* Overload tuple linked list to put us in template list. */
hlist_nulls_add_head_rcu(&tmpl->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
&pcpu->tmpl);
@@ -921,11 +925,9 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
/* Now it is inserted into the unconfirmed list, bump refcount */
nf_conntrack_get(&ct->ct_general);
-
- spin_unlock_bh(&nf_conntrack_lock);
-
nf_ct_add_to_unconfirmed_list(ct);
+ spin_unlock_bh(&nf_conntrack_lock);
if (exp) {
if (exp->expectfn)
--
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