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Date: Mon, 6 Jul 2015 05:18:09 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...mgrid.com>,
Jamal Hadi Salim <jhs@...atatu.com>,
John Fastabend <john.fastabend@...il.com>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <edumazet@...il.com>
Subject: [PATCH v3 net-next 7/7] net_sched: act_mirred: remove spinlock in fast path
Like act_gact, act_mirred can be lockless in packet processing
1) Use percpu stats
2) update lastuse only every clock tick to avoid false sharing
3) use rcu to protect tcfm_dev
4) Remove spinlock usage, as it is no longer needed.
Next step : add multi queue capability to ifb device
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>
Cc: John Fastabend <john.fastabend@...il.com>
---
include/net/tc_act/tc_mirred.h | 2 +-
net/sched/act_mirred.c | 57 ++++++++++++++++++++++--------------------
2 files changed, 31 insertions(+), 28 deletions(-)
diff --git a/include/net/tc_act/tc_mirred.h b/include/net/tc_act/tc_mirred.h
index 4dd77a1c106b..dae96bae1c19 100644
--- a/include/net/tc_act/tc_mirred.h
+++ b/include/net/tc_act/tc_mirred.h
@@ -8,7 +8,7 @@ struct tcf_mirred {
int tcfm_eaction;
int tcfm_ifindex;
int tcfm_ok_push;
- struct net_device *tcfm_dev;
+ struct net_device __rcu *tcfm_dev;
struct list_head tcfm_list;
};
#define to_mirred(a) \
diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 002cd6c83dc6..19cd8904efa0 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -35,9 +35,11 @@ static LIST_HEAD(mirred_list);
static void tcf_mirred_release(struct tc_action *a, int bind)
{
struct tcf_mirred *m = to_mirred(a);
+ struct net_device *dev = rcu_dereference_protected(m->tcfm_dev, 1);
+
list_del(&m->tcfm_list);
- if (m->tcfm_dev)
- dev_put(m->tcfm_dev);
+ if (dev)
+ dev_put(dev);
}
static const struct nla_policy mirred_policy[TCA_MIRRED_MAX + 1] = {
@@ -94,7 +96,7 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
if (dev == NULL)
return -EINVAL;
ret = tcf_hash_create(parm->index, est, a, sizeof(*m),
- bind, false);
+ bind, true);
if (ret)
return ret;
ret = ACT_P_CREATED;
@@ -106,18 +108,18 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
}
m = to_mirred(a);
- spin_lock_bh(&m->tcf_lock);
+ ASSERT_RTNL();
m->tcf_action = parm->action;
m->tcfm_eaction = parm->eaction;
if (dev != NULL) {
m->tcfm_ifindex = parm->ifindex;
if (ret != ACT_P_CREATED)
- dev_put(m->tcfm_dev);
+ dev_put(rcu_dereference_protected(m->tcfm_dev, 1));
dev_hold(dev);
- m->tcfm_dev = dev;
+ rcu_assign_pointer(m->tcfm_dev, dev);
m->tcfm_ok_push = ok_push;
}
- spin_unlock_bh(&m->tcf_lock);
+
if (ret == ACT_P_CREATED) {
list_add(&m->tcfm_list, &mirred_list);
tcf_hash_insert(a);
@@ -132,20 +134,22 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
struct tcf_mirred *m = a->priv;
struct net_device *dev;
struct sk_buff *skb2;
+ int retval, err;
u32 at;
- int retval, err = 1;
- spin_lock(&m->tcf_lock);
- m->tcf_tm.lastuse = jiffies;
- bstats_update(&m->tcf_bstats, skb);
+ tcf_lastuse_update(&m->tcf_tm);
+
+ bstats_cpu_update(this_cpu_ptr(m->common.cpu_bstats), skb);
- dev = m->tcfm_dev;
- if (!dev) {
- printk_once(KERN_NOTICE "tc mirred: target device is gone\n");
+ rcu_read_lock();
+ retval = READ_ONCE(m->tcf_action);
+ dev = rcu_dereference(m->tcfm_dev);
+ if (unlikely(!dev)) {
+ pr_notice_once("tc mirred: target device is gone\n");
goto out;
}
- if (!(dev->flags & IFF_UP)) {
+ if (unlikely(!(dev->flags & IFF_UP))) {
net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
dev->name);
goto out;
@@ -153,7 +157,7 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
at = G_TC_AT(skb->tc_verd);
skb2 = skb_clone(skb, GFP_ATOMIC);
- if (skb2 == NULL)
+ if (!skb2)
goto out;
if (!(at & AT_EGRESS)) {
@@ -169,16 +173,13 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
skb2->dev = dev;
err = dev_queue_xmit(skb2);
-out:
if (err) {
- m->tcf_qstats.overlimits++;
+out:
+ qstats_overlimit_inc(this_cpu_ptr(m->common.cpu_qstats));
if (m->tcfm_eaction != TCA_EGRESS_MIRROR)
retval = TC_ACT_SHOT;
- else
- retval = m->tcf_action;
- } else
- retval = m->tcf_action;
- spin_unlock(&m->tcf_lock);
+ }
+ rcu_read_unlock();
return retval;
}
@@ -217,14 +218,16 @@ static int mirred_device_event(struct notifier_block *unused,
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct tcf_mirred *m;
+ ASSERT_RTNL();
if (event == NETDEV_UNREGISTER)
list_for_each_entry(m, &mirred_list, tcfm_list) {
- spin_lock_bh(&m->tcf_lock);
- if (m->tcfm_dev == dev) {
+ if (rcu_access_pointer(m->tcfm_dev) == dev) {
dev_put(dev);
- m->tcfm_dev = NULL;
+ /* Note : no rcu grace period necessary, as
+ * net_device are already rcu protected.
+ */
+ RCU_INIT_POINTER(m->tcfm_dev, NULL);
}
- spin_unlock_bh(&m->tcf_lock);
}
return NOTIFY_DONE;
--
2.4.3.573.g4eafbef
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