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Merge branch 'act_csum-spinlock-remove'

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Davide Caratti says:

====================
net/sched: remove spinlock from 'csum' action

Similarly to what has been done earlier with other actions [1][2], this
series tries to improve the performance of 'csum' tc action, removing a
spinlock in the data path. Patch 1 lets act_csum use per-CPU counters;
patch 2 removes spin_{,un}lock_bh() calls from the act() method.

test procedure (using pktgen from https://github.com/netoptimizer):

 # ip link add name eth1 type dummy
 # ip link set dev eth1 up
 # tc qdisc add dev eth1 root handle 1: prio
 # for a in pass drop; do
 > tc filter del dev eth1 parent 1: pref 10 matchall action csum udp
 > tc filter add dev eth1 parent 1: pref 10 matchall action csum udp $a
 > for n in 2 4; do
 > ./pktgen_bench_xmit_mode_queue_xmit.sh -v -s 64 -t $n -n 1000000 -i eth1
 > done
 > done

test results:

      |    |  before patch   |   after patch
  $a  | $n | avg. pps/thread | avg. pps/thread
 -----+----+-----------------+----------------
 pass |  2 |    1671463 ± 4% |    1920789 ± 3%
 pass |  4 |     648797 ± 1% |     738190 ± 1%
 drop |  2 |    3212692 ± 2% |    3719811 ± 2%
 drop |  4 |    1078824 ± 1% |    1328099 ± 1%

references:

[1] https://www.spinics.net/lists/netdev/msg334760.html
[2] https://www.spinics.net/lists/netdev/msg465862.html

v3 changes:
 - use rtnl_dereference() in place of rcu_dereference() in tcf_csum_dump()

v2 changes:
 - add 'drop' test, it produces more contentions
 - use RCU-protected struct to store 'action' and 'update_flags', to avoid
   reading the values from subsequent configurations
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2018-01-23 19:51:46 -05:00
commit 6b44d0f9c9
2 changed files with 62 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
include/net/tc_act/tc_csum.h
View File

@ -6,10 +6,16 @@
#include <net/act_api.h>
#include <linux/tc_act/tc_csum.h>
struct tcf_csum_params {
int action;
u32 update_flags;
struct rcu_head rcu;
};
struct tcf_csum {
struct tc_action common;
u32 update_flags;
struct tcf_csum_params __rcu *params;
};
#define to_tcf_csum(a) ((struct tcf_csum *)a)
@ -24,7 +30,13 @@ static inline bool is_tcf_csum(const struct tc_action *a)
static inline u32 tcf_csum_update_flags(const struct tc_action *a)
{
return to_tcf_csum(a)->update_flags;
u32 update_flags;
rcu_read_lock();
update_flags = rcu_dereference(to_tcf_csum(a)->params)->update_flags;
rcu_read_unlock();
return update_flags;
}
#endif /* __NET_TC_CSUM_H */

66
net/sched/act_csum.c
View File

@ -49,6 +49,7 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla,
int bind)
{
struct tc_action_net *tn = net_generic(net, csum_net_id);
struct tcf_csum_params *params_old, *params_new;
struct nlattr *tb[TCA_CSUM_MAX + 1];
struct tc_csum *parm;
struct tcf_csum *p;
@ -67,7 +68,7 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla,
if (!tcf_idr_check(tn, parm->index, a, bind)) {
ret = tcf_idr_create(tn, parm->index, est, a,
&act_csum_ops, bind, false);
&act_csum_ops, bind, true);
if (ret)
return ret;
ret = ACT_P_CREATED;
@ -80,10 +81,21 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla,
}
p = to_tcf_csum(*a);
spin_lock_bh(&p->tcf_lock);
p->tcf_action = parm->action;
p->update_flags = parm->update_flags;
spin_unlock_bh(&p->tcf_lock);
ASSERT_RTNL();
params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
if (unlikely(!params_new)) {
if (ret == ACT_P_CREATED)
tcf_idr_release(*a, bind);
return -ENOMEM;
}
params_old = rtnl_dereference(p->params);
params_new->action = parm->action;
params_new->update_flags = parm->update_flags;
rcu_assign_pointer(p->params, params_new);
if (params_old)
kfree_rcu(params_old, rcu);
if (ret == ACT_P_CREATED)
tcf_idr_insert(tn, *a);
@ -539,19 +551,21 @@ static int tcf_csum(struct sk_buff *skb, const struct tc_action *a,
struct tcf_result *res)
{
struct tcf_csum *p = to_tcf_csum(a);
int action;
struct tcf_csum_params *params;
u32 update_flags;
int action;
rcu_read_lock();
params = rcu_dereference(p->params);
spin_lock(&p->tcf_lock);
tcf_lastuse_update(&p->tcf_tm);
bstats_update(&p->tcf_bstats, skb);
action = p->tcf_action;
update_flags = p->update_flags;
spin_unlock(&p->tcf_lock);
bstats_cpu_update(this_cpu_ptr(p->common.cpu_bstats), skb);
action = params->action;
if (unlikely(action == TC_ACT_SHOT))
goto drop;
goto drop_stats;
update_flags = params->update_flags;
switch (tc_skb_protocol(skb)) {
case cpu_to_be16(ETH_P_IP):
if (!tcf_csum_ipv4(skb, update_flags))
@ -563,13 +577,16 @@ static int tcf_csum(struct sk_buff *skb, const struct tc_action *a,
break;
}
unlock:
rcu_read_unlock();
return action;
drop:
spin_lock(&p->tcf_lock);
p->tcf_qstats.drops++;
spin_unlock(&p->tcf_lock);
return TC_ACT_SHOT;
action = TC_ACT_SHOT;
drop_stats:
qstats_drop_inc(this_cpu_ptr(p->common.cpu_qstats));
goto unlock;
}
static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
@ -577,15 +594,18 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
{
unsigned char *b = skb_tail_pointer(skb);
struct tcf_csum *p = to_tcf_csum(a);
struct tcf_csum_params *params;
struct tc_csum opt = {
.update_flags = p->update_flags,
.index = p->tcf_index,
.action = p->tcf_action,
.refcnt = p->tcf_refcnt - ref,
.bindcnt = p->tcf_bindcnt - bind,
};
struct tcf_t t;
params = rtnl_dereference(p->params);
opt.action = params->action;
opt.update_flags = params->update_flags;
if (nla_put(skb, TCA_CSUM_PARMS, sizeof(opt), &opt))
goto nla_put_failure;
@ -600,6 +620,15 @@ nla_put_failure:
return -1;
}
static void tcf_csum_cleanup(struct tc_action *a)
{
struct tcf_csum *p = to_tcf_csum(a);
struct tcf_csum_params *params;
params = rcu_dereference_protected(p->params, 1);
kfree_rcu(params, rcu);
}
static int tcf_csum_walker(struct net *net, struct sk_buff *skb,
struct netlink_callback *cb, int type,
const struct tc_action_ops *ops)
@ -623,6 +652,7 @@ static struct tc_action_ops act_csum_ops = {
.act = tcf_csum,
.dump = tcf_csum_dump,
.init = tcf_csum_init,
.cleanup = tcf_csum_cleanup,
.walk = tcf_csum_walker,
.lookup = tcf_csum_search,
.size = sizeof(struct tcf_csum),