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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@google.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-07-06 05:18:09 -07:00 committed by David S. Miller
parent 56e5d1ca18
commit 2ee22a90c7
2 changed files with 31 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/tc_act/tc_mirred.h
View File

@ -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) \

57
net/sched/act_mirred.c
View File

@ -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);
dev = m->tcfm_dev;
if (!dev) {
printk_once(KERN_NOTICE "tc mirred: target device is gone\n");
bstats_cpu_update(this_cpu_ptr(m->common.cpu_bstats), skb);
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;