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Message-ID: <20171011131318.GF2039@nanopsycho>
Date: Wed, 11 Oct 2017 15:13:18 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Manish Kurup <kurup.manish@...il.com>
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, davem@...emloft.net,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
aring@...atatu.com, mrv@...atatu.com, manish.kurup@...izon.com
Subject: Re: [PATCH net-next 2/2] net sched act_vlan: VLAN action rewrite to
use RCU lock/unlock and update
Wed, Oct 11, 2017 at 04:33:39AM CEST, kurup.manish@...il.com wrote:
>Using a spinlock in the VLAN action causes performance issues when the VLAN
>action is used on multiple cores. Rewrote the VLAN action to use RCU read
>locking for reads and updates instead.
>
>Signed-off-by: Manish Kurup <manish.kurup@...izon.com>
>---
> include/net/tc_act/tc_vlan.h | 21 ++++++++-----
> net/sched/act_vlan.c | 73 ++++++++++++++++++++++++++++++--------------
> 2 files changed, 63 insertions(+), 31 deletions(-)
>
>diff --git a/include/net/tc_act/tc_vlan.h b/include/net/tc_act/tc_vlan.h
>index c2090df..67fd355 100644
>--- a/include/net/tc_act/tc_vlan.h
>+++ b/include/net/tc_act/tc_vlan.h
>@@ -13,12 +13,17 @@
> #include <net/act_api.h>
> #include <linux/tc_act/tc_vlan.h>
>
>+struct tcf_vlan_params {
>+ struct rcu_head rcu;
Usually rcu_head is put at the very end of struct.
>+ int tcfv_action;
>+ u16 tcfv_push_vid;
>+ __be16 tcfv_push_proto;
>+ u8 tcfv_push_prio;
>+};
>+
> struct tcf_vlan {
> struct tc_action common;
>- int tcfv_action;
>- u16 tcfv_push_vid;
>- __be16 tcfv_push_proto;
>- u8 tcfv_push_prio;
>+ struct tcf_vlan_params __rcu *vlan_p;
> };
> #define to_vlan(a) ((struct tcf_vlan *)a)
>
>@@ -33,22 +38,22 @@ static inline bool is_tcf_vlan(const struct tc_action *a)
>
> static inline u32 tcf_vlan_action(const struct tc_action *a)
> {
>- return to_vlan(a)->tcfv_action;
>+ return to_vlan(a)->vlan_p->tcfv_action;
> }
>
> static inline u16 tcf_vlan_push_vid(const struct tc_action *a)
> {
>- return to_vlan(a)->tcfv_push_vid;
>+ return to_vlan(a)->vlan_p->tcfv_push_vid;
> }
>
> static inline __be16 tcf_vlan_push_proto(const struct tc_action *a)
> {
>- return to_vlan(a)->tcfv_push_proto;
>+ return to_vlan(a)->vlan_p->tcfv_push_proto;
> }
>
> static inline u8 tcf_vlan_push_prio(const struct tc_action *a)
> {
>- return to_vlan(a)->tcfv_push_prio;
>+ return to_vlan(a)->vlan_p->tcfv_push_prio;
All these helpers should use rtnl_dereference() as well
> }
>
> #endif /* __NET_TC_VLAN_H */
>diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c
>index 14c262c..9bb0236 100644
>--- a/net/sched/act_vlan.c
>+++ b/net/sched/act_vlan.c
>@@ -29,31 +29,37 @@ static int tcf_vlan(struct sk_buff *skb, const struct tc_action *a,
> int action;
> int err;
> u16 tci;
>+ struct tcf_vlan_params *p;
>
> tcf_lastuse_update(&v->tcf_tm);
> bstats_cpu_update(this_cpu_ptr(v->common.cpu_bstats), skb);
>
>- spin_lock(&v->tcf_lock);
>- action = v->tcf_action;
>-
> /* Ensure 'data' points at mac_header prior calling vlan manipulating
> * functions.
> */
> if (skb_at_tc_ingress(skb))
> skb_push_rcsum(skb, skb->mac_len);
>
>- switch (v->tcfv_action) {
>+ rcu_read_lock();
>+
>+ action = READ_ONCE(v->tcf_action);
>+
Too many empty lines. At least remove the one above this ^
>+ p = rcu_dereference(v->vlan_p);
>+
>+ switch (p->tcfv_action) {
> case TCA_VLAN_ACT_POP:
> err = skb_vlan_pop(skb);
> if (err)
> goto drop;
> break;
>+
> case TCA_VLAN_ACT_PUSH:
>- err = skb_vlan_push(skb, v->tcfv_push_proto, v->tcfv_push_vid |
>- (v->tcfv_push_prio << VLAN_PRIO_SHIFT));
>+ err = skb_vlan_push(skb, p->tcfv_push_proto, p->tcfv_push_vid |
>+ (p->tcfv_push_prio << VLAN_PRIO_SHIFT));
Again, indentation is odd. Please fix.
> if (err)
> goto drop;
> break;
>+
Avoid adding this unrelated empty line.
> case TCA_VLAN_ACT_MODIFY:
> /* No-op if no vlan tag (either hw-accel or in-payload) */
> if (!skb_vlan_tagged(skb))
>@@ -69,15 +75,16 @@ static int tcf_vlan(struct sk_buff *skb, const struct tc_action *a,
> goto drop;
> }
> /* replace the vid */
>- tci = (tci & ~VLAN_VID_MASK) | v->tcfv_push_vid;
>+ tci = (tci & ~VLAN_VID_MASK) | p->tcfv_push_vid;
> /* replace prio bits, if tcfv_push_prio specified */
>- if (v->tcfv_push_prio) {
>+ if (p->tcfv_push_prio) {
> tci &= ~VLAN_PRIO_MASK;
>- tci |= v->tcfv_push_prio << VLAN_PRIO_SHIFT;
>+ tci |= p->tcfv_push_prio << VLAN_PRIO_SHIFT;
> }
> /* put updated tci as hwaccel tag */
>- __vlan_hwaccel_put_tag(skb, v->tcfv_push_proto, tci);
>+ __vlan_hwaccel_put_tag(skb, p->tcfv_push_proto, tci);
> break;
>+
Again, avoid adding this unrelated empty line.
> default:
> BUG();
> }
>@@ -89,6 +96,7 @@ static int tcf_vlan(struct sk_buff *skb, const struct tc_action *a,
> qstats_drop_inc(this_cpu_ptr(v->common.cpu_qstats));
>
> unlock:
>+ rcu_read_unlock();
> if (skb_at_tc_ingress(skb))
> skb_pull_rcsum(skb, skb->mac_len);
>
>@@ -111,6 +119,7 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
> struct nlattr *tb[TCA_VLAN_MAX + 1];
> struct tc_vlan *parm;
> struct tcf_vlan *v;
>+ struct tcf_vlan_params *p, *p_old;
The famous reverse-christmas-tree rule dictates this to be put right
above "struct tc_vlan *parm" :)
> int action;
> __be16 push_vid = 0;
> __be16 push_proto = 0;
>@@ -187,16 +196,33 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
>
> v = to_vlan(*a);
>
>- spin_lock_bh(&v->tcf_lock);
>-
>- v->tcfv_action = action;
>- v->tcfv_push_vid = push_vid;
>- v->tcfv_push_prio = push_prio;
>- v->tcfv_push_proto = push_proto;
>+ ASSERT_RTNL();
>+ p = kzalloc(sizeof(*p), GFP_KERNEL);
>+ if (unlikely(!p)) {
>+ if (ovr)
>+ tcf_idr_release(*a, bind);
>+ return -ENOMEM;
>+ }
>
> v->tcf_action = parm->action;
>
>- spin_unlock_bh(&v->tcf_lock);
>+ p_old = rtnl_dereference(v->vlan_p);
>+
>+ if (ovr)
>+ spin_lock_bh(&v->tcf_lock);
>+
>+ p->tcfv_action = action;
>+ p->tcfv_push_vid = push_vid;
>+ p->tcfv_push_prio = push_prio;
>+ p->tcfv_push_proto = push_proto;
>+
>+ rcu_assign_pointer(v->vlan_p, p);
>+
>+ if (ovr)
>+ spin_unlock_bh(&v->tcf_lock);
>+
>+ if (p_old)
>+ kfree_rcu(p_old, rcu);
>
> if (ret == ACT_P_CREATED)
> tcf_idr_insert(tn, *a);
>@@ -208,25 +234,26 @@ static int tcf_vlan_dump(struct sk_buff *skb, struct tc_action *a,
> {
> unsigned char *b = skb_tail_pointer(skb);
> struct tcf_vlan *v = to_vlan(a);
>+ struct tcf_vlan_params *p = rtnl_dereference(v->vlan_p);
> struct tc_vlan opt = {
> .index = v->tcf_index,
> .refcnt = v->tcf_refcnt - ref,
> .bindcnt = v->tcf_bindcnt - bind,
> .action = v->tcf_action,
>- .v_action = v->tcfv_action,
>+ .v_action = p->tcfv_action,
> };
> struct tcf_t t;
>
> if (nla_put(skb, TCA_VLAN_PARMS, sizeof(opt), &opt))
> goto nla_put_failure;
>
>- if ((v->tcfv_action == TCA_VLAN_ACT_PUSH ||
>- v->tcfv_action == TCA_VLAN_ACT_MODIFY) &&
>- (nla_put_u16(skb, TCA_VLAN_PUSH_VLAN_ID, v->tcfv_push_vid) ||
>+ if ((p->tcfv_action == TCA_VLAN_ACT_PUSH ||
>+ p->tcfv_action == TCA_VLAN_ACT_MODIFY) &&
>+ (nla_put_u16(skb, TCA_VLAN_PUSH_VLAN_ID, p->tcfv_push_vid) ||
> nla_put_be16(skb, TCA_VLAN_PUSH_VLAN_PROTOCOL,
>- v->tcfv_push_proto) ||
>+ p->tcfv_push_proto) ||
> (nla_put_u8(skb, TCA_VLAN_PUSH_VLAN_PRIORITY,
>- v->tcfv_push_prio))))
>+ p->tcfv_push_prio))))
> goto nla_put_failure;
>
> tcf_tm_dump(&t, &v->tcf_tm);
>--
>2.7.4
>
Besides the couple of nits I pointed out, this looks nice. Thanks!
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