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Message-ID: <20171101152506.vjhhloswfyoycb2v@netronome.com>
Date: Wed, 1 Nov 2017 16:25:07 +0100
From: Simon Horman <simon.horman@...ronome.com>
To: Manish Kurup <kurup.manish@...il.com>
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
jakub.kicinski@...ronome.com, pieter.jansenvanvuuren@...ronome.com,
john.hurley@...ronome.com, oss-drivers@...ronome.com,
davem@...emloft.net, netdev@...r.kernel.org, aring@...atatu.com,
mrv@...atatu.com, Manish Kurup <manish.kurup@...izon.com>
Subject: Re: [PATCH net-next v4 3/3] net sched act_vlan: VLAN action rewrite
to use RCU lock/unlock and update
On Tue, Oct 31, 2017 at 02:17:00PM -0400, Manish Kurup 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.
>
> Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
> Acked-by: Jiri Pirko <jiri@...lanox.com>
> Signed-off-by: Manish Kurup <manish.kurup@...izon.com>
> ---
> include/net/tc_act/tc_vlan.h | 46 +++++++++++++++++++++++++------
> net/sched/act_vlan.c | 65 ++++++++++++++++++++++++++++----------------
> 2 files changed, 78 insertions(+), 33 deletions(-)
>
> diff --git a/include/net/tc_act/tc_vlan.h b/include/net/tc_act/tc_vlan.h
> index c2090df..22ae260 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 {
> + int tcfv_action;
> + u16 tcfv_push_vid;
> + __be16 tcfv_push_proto;
> + u8 tcfv_push_prio;
> + struct rcu_head rcu;
> +};
> +
> 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 +38,45 @@ 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;
> + u32 tcfv_action;
> +
> + rcu_read_lock();
> + tcfv_action = rcu_dereference(to_vlan(a)->vlan_p)->tcfv_action;
> + rcu_read_unlock();
> +
> + return tcfv_action;
> }
>
> static inline u16 tcf_vlan_push_vid(const struct tc_action *a)
> {
> - return to_vlan(a)->tcfv_push_vid;
> + u16 tcfv_push_vid;
> +
> + rcu_read_lock();
> + tcfv_push_vid = rcu_dereference(to_vlan(a)->vlan_p)->tcfv_push_vid;
> + rcu_read_unlock();
> +
> + return tcfv_push_vid;
> }
>
> static inline __be16 tcf_vlan_push_proto(const struct tc_action *a)
> {
> - return to_vlan(a)->tcfv_push_proto;
> + __be16 tcfv_push_proto;
> +
> + rcu_read_lock();
> + tcfv_push_proto = rcu_dereference(to_vlan(a)->vlan_p)->tcfv_push_proto;
> + rcu_read_unlock();
> +
> + return tcfv_push_proto;
> }
>
> static inline u8 tcf_vlan_push_prio(const struct tc_action *a)
> {
> - return to_vlan(a)->tcfv_push_prio;
> -}
> + u8 tcfv_push_prio;
>
> + rcu_read_lock();
> + tcfv_push_prio = rcu_dereference(to_vlan(a)->vlan_p)->tcfv_push_prio;
> + rcu_read_unlock();
> +
> + return tcfv_push_prio;
> +}
> #endif /* __NET_TC_VLAN_H */
> diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c
> index b093bad..7f461f9 100644
> --- a/net/sched/act_vlan.c
> +++ b/net/sched/act_vlan.c
> @@ -26,6 +26,7 @@ static int tcf_vlan(struct sk_buff *skb, const struct tc_action *a,
> struct tcf_result *res)
> {
> struct tcf_vlan *v = to_vlan(a);
> + struct tcf_vlan_params *p;
> int action;
> int err;
> u16 tci;
> @@ -33,24 +34,27 @@ static int tcf_vlan(struct sk_buff *skb, const struct tc_action *a,
> 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);
> +
> + p = rcu_dereference(v->vlan_p);
> +
> + switch (p->tcfv_action) {
Its not clear to me why v->tcfv_action is changed to p->tcfv_action here.
> 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));
> if (err)
> goto drop;
> break;
> @@ -69,14 +73,14 @@ 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;
> default:
> BUG();
> @@ -89,10 +93,10 @@ 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);
>
> - spin_unlock(&v->tcf_lock);
> return action;
> }
>
> @@ -109,6 +113,7 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
> {
> struct tc_action_net *tn = net_generic(net, vlan_net_id);
> struct nlattr *tb[TCA_VLAN_MAX + 1];
> + struct tcf_vlan_params *p, *p_old;
> struct tc_vlan *parm;
> struct tcf_vlan *v;
> int action;
> @@ -187,16 +192,27 @@ 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)) {
I don't think its usual to use unlikely to handle allocation errors
in the control plane. I'd remove it from here.
> + 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);
> +
> + 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 (p_old)
> + kfree_rcu(p_old, rcu);
>
> if (ret == ACT_P_CREATED)
> tcf_idr_insert(tn, *a);
> @@ -208,25 +224,26 @@ 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
>
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