Message-Id: <20230127192752.3643015-1-pctammela@mojatatu.com>
Date:   Fri, 27 Jan 2023 16:27:52 -0300
From:   Pedro Tammela <pctammela@...atatu.com>
To:     netdev@...r.kernel.org
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, Pedro Tammela <pctammela@...atatu.com>
Subject: [PATCH net-next v3] net/sched: transition act_pedit to rcu and percpu stats

The software pedit action didn't get the same love as some of the
other actions and it's still using spinlocks and shared stats.
Transition the action to rcu and percpu stats which improves the
action's performance dramatically.

We test this change with a very simple packet forwarding setup:

tc filter add dev ens2f0 ingress protocol ip matchall \
   action pedit ex munge eth src set b8:ce:f6:4b:68:35 pipe \
   action pedit ex munge eth dst set ac:1f:6b:e4:ff:93 pipe \
   action mirred egress redirect dev ens2f1
tc filter add dev ens2f1 ingress protocol ip matchall \
   action pedit ex munge eth src set b8:ce:f6:4b:68:34 pipe \
   action pedit ex munge eth dst set ac:1f:6b:e4:ff:92 pipe \
   action mirred egress redirect dev ens2f0

Using TRex with a http-like profile, in our setup with a 25G NIC
and a 26 cores Intel CPU, we observe the following in perf:
   before:
    11.59%  2.30%  [kernel]  [k] tcf_pedit_act
       2.55% tcf_pedit_act
	     8.38% _raw_spin_lock
		       6.43% native_queued_spin_lock_slowpath
   after:
    1.46%  1.46%  [kernel]  [k] tcf_pedit_act

Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>

v2->v3:
- Add missing change in act idr create

v1->v2:
- Fix lock unbalance found by sparse

---
 include/net/tc_act/tc_pedit.h |  81 ++++++++--
 net/sched/act_pedit.c         | 273 +++++++++++++++++++---------------
 2 files changed, 217 insertions(+), 137 deletions(-)

diff --git a/include/net/tc_act/tc_pedit.h b/include/net/tc_act/tc_pedit.h
index 3e02709a1df6..7c597db2b4fa 100644
--- a/include/net/tc_act/tc_pedit.h
+++ b/include/net/tc_act/tc_pedit.h
@@ -4,22 +4,29 @@
 
 #include <net/act_api.h>
 #include <linux/tc_act/tc_pedit.h>
+#include <linux/types.h>
 
 struct tcf_pedit_key_ex {
 	enum pedit_header_type htype;
 	enum pedit_cmd cmd;
 };
 
-struct tcf_pedit {
-	struct tc_action	common;
-	unsigned char		tcfp_nkeys;
-	unsigned char		tcfp_flags;
-	u32			tcfp_off_max_hint;
+struct tcf_pedit_parms {
 	struct tc_pedit_key	*tcfp_keys;
 	struct tcf_pedit_key_ex	*tcfp_keys_ex;
+	u32			tcfp_off_max_hint;
+	unsigned char		tcfp_nkeys;
+	unsigned char		tcfp_flags;
+	struct rcu_head	rcu;
+};
+
+struct tcf_pedit {
+	struct tc_action common;
+	struct tcf_pedit_parms __rcu *parms;
 };
 
 #define to_pedit(a) ((struct tcf_pedit *)a)
+#define to_pedit_parms(a) (rcu_dereference(to_pedit(a)->parms))
 
 static inline bool is_tcf_pedit(const struct tc_action *a)
 {
@@ -32,37 +39,81 @@ static inline bool is_tcf_pedit(const struct tc_action *a)
 
 static inline int tcf_pedit_nkeys(const struct tc_action *a)
 {
-	return to_pedit(a)->tcfp_nkeys;
+	struct tcf_pedit_parms *parms;
+	int nkeys;
+
+	rcu_read_lock();
+	parms = to_pedit_parms(a);
+	nkeys = parms->tcfp_nkeys;
+	rcu_read_unlock();
+
+	return nkeys;
 }
 
 static inline u32 tcf_pedit_htype(const struct tc_action *a, int index)
 {
-	if (to_pedit(a)->tcfp_keys_ex)
-		return to_pedit(a)->tcfp_keys_ex[index].htype;
+	struct tcf_pedit_parms *parms;
+	u32 htype = TCA_PEDIT_KEY_EX_HDR_TYPE_NETWORK;
+
+	rcu_read_lock();
+	parms = to_pedit_parms(a);
+	if (parms->tcfp_keys_ex)
+		htype = parms->tcfp_keys_ex[index].htype;
+	rcu_read_unlock();
 
-	return TCA_PEDIT_KEY_EX_HDR_TYPE_NETWORK;
+	return htype;
 }
 
 static inline u32 tcf_pedit_cmd(const struct tc_action *a, int index)
 {
-	if (to_pedit(a)->tcfp_keys_ex)
-		return to_pedit(a)->tcfp_keys_ex[index].cmd;
+	struct tcf_pedit_parms *parms;
+	u32 cmd = __PEDIT_CMD_MAX;
 
-	return __PEDIT_CMD_MAX;
+	rcu_read_lock();
+	parms = to_pedit_parms(a);
+	if (parms->tcfp_keys_ex)
+		cmd = parms->tcfp_keys_ex[index].cmd;
+	rcu_read_unlock();
+
+	return cmd;
 }
 
 static inline u32 tcf_pedit_mask(const struct tc_action *a, int index)
 {
-	return to_pedit(a)->tcfp_keys[index].mask;
+	struct tcf_pedit_parms *parms;
+	u32 mask;
+
+	rcu_read_lock();
+	parms = to_pedit_parms(a);
+	mask = parms->tcfp_keys[index].mask;
+	rcu_read_unlock();
+
+	return mask;
 }
 
 static inline u32 tcf_pedit_val(const struct tc_action *a, int index)
 {
-	return to_pedit(a)->tcfp_keys[index].val;
+	struct tcf_pedit_parms *parms;
+	u32 val;
+
+	rcu_read_lock();
+	parms = to_pedit_parms(a);
+	val = parms->tcfp_keys[index].val;
+	rcu_read_unlock();
+
+	return val;
 }
 
 static inline u32 tcf_pedit_offset(const struct tc_action *a, int index)
 {
-	return to_pedit(a)->tcfp_keys[index].off;
+	struct tcf_pedit_parms *parms;
+	u32 off;
+
+	rcu_read_lock();
+	parms = to_pedit_parms(a);
+	off = parms->tcfp_keys[index].off;
+	rcu_read_unlock();
+
+	return off;
 }
 #endif /* __NET_TC_PED_H */
diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index a0378e9f0121..1b3499585d7a 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -134,6 +134,17 @@ static int tcf_pedit_key_ex_dump(struct sk_buff *skb,
 	return -EINVAL;
 }
 
+static void tcf_pedit_cleanup_rcu(struct rcu_head *head)
+{
+	struct tcf_pedit_parms *parms =
+		container_of(head, struct tcf_pedit_parms, rcu);
+
+	kfree(parms->tcfp_keys_ex);
+	kfree(parms->tcfp_keys);
+
+	kfree(parms);
+}
+
 static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 			  struct nlattr *est, struct tc_action **a,
 			  struct tcf_proto *tp, u32 flags,
@@ -143,8 +154,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 	bool bind = flags & TCA_ACT_FLAGS_BIND;
 	struct nlattr *tb[TCA_PEDIT_MAX + 1];
 	struct tcf_chain *goto_ch = NULL;
-	struct tc_pedit_key *keys = NULL;
-	struct tcf_pedit_key_ex *keys_ex;
+	struct tcf_pedit_parms *oparms, *nparms;
 	struct tc_pedit *parm;
 	struct nlattr *pattr;
 	struct tcf_pedit *p;
@@ -181,18 +191,25 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 		return -EINVAL;
 	}
 
-	keys_ex = tcf_pedit_keys_ex_parse(tb[TCA_PEDIT_KEYS_EX], parm->nkeys);
-	if (IS_ERR(keys_ex))
-		return PTR_ERR(keys_ex);
+	nparms = kzalloc(sizeof(*nparms), GFP_KERNEL);
+	if (!nparms)
+		return -ENOMEM;
+
+	nparms->tcfp_keys_ex =
+		tcf_pedit_keys_ex_parse(tb[TCA_PEDIT_KEYS_EX], parm->nkeys);
+	if (IS_ERR(nparms->tcfp_keys_ex)) {
+		ret = PTR_ERR(nparms->tcfp_keys_ex);
+		goto out_free;
+	}
 
 	index = parm->index;
 	err = tcf_idr_check_alloc(tn, &index, a, bind);
 	if (!err) {
-		ret = tcf_idr_create(tn, index, est, a,
-				     &act_pedit_ops, bind, false, flags);
+		ret = tcf_idr_create_from_flags(tn, index, est, a,
+						&act_pedit_ops, bind, flags);
 		if (ret) {
 			tcf_idr_cleanup(tn, index);
-			goto out_free;
+			goto out_free_ex;
 		}
 		ret = ACT_P_CREATED;
 	} else if (err > 0) {
@@ -204,7 +221,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 		}
 	} else {
 		ret = err;
-		goto out_free;
+		goto out_free_ex;
 	}
 
 	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
@@ -212,68 +229,79 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 		ret = err;
 		goto out_release;
 	}
+
+	nparms->tcfp_off_max_hint = 0;
+	nparms->tcfp_flags = parm->flags;
+
 	p = to_pedit(*a);
 	spin_lock_bh(&p->tcf_lock);
 
+	oparms = rcu_dereference_protected(p->parms, 1);
+
 	if (ret == ACT_P_CREATED ||
-	    (p->tcfp_nkeys && p->tcfp_nkeys != parm->nkeys)) {
-		keys = kmalloc(ksize, GFP_ATOMIC);
-		if (!keys) {
+	    (oparms->tcfp_nkeys && oparms->tcfp_nkeys != parm->nkeys)) {
+		nparms->tcfp_keys = kmalloc(ksize, GFP_ATOMIC);
+		if (!nparms->tcfp_keys) {
 			spin_unlock_bh(&p->tcf_lock);
 			ret = -ENOMEM;
-			goto put_chain;
+			goto out_release;
 		}
-		kfree(p->tcfp_keys);
-		p->tcfp_keys = keys;
-		p->tcfp_nkeys = parm->nkeys;
+		nparms->tcfp_nkeys = parm->nkeys;
+	} else {
+		nparms->tcfp_keys = oparms->tcfp_keys;
+		nparms->tcfp_nkeys = oparms->tcfp_nkeys;
 	}
-	memcpy(p->tcfp_keys, parm->keys, ksize);
-	p->tcfp_off_max_hint = 0;
-	for (i = 0; i < p->tcfp_nkeys; ++i) {
-		u32 cur = p->tcfp_keys[i].off;
+
+	memcpy(nparms->tcfp_keys, parm->keys, ksize);
+
+	for (i = 0; i < nparms->tcfp_nkeys; ++i) {
+		u32 cur = nparms->tcfp_keys[i].off;
 
 		/* sanitize the shift value for any later use */
-		p->tcfp_keys[i].shift = min_t(size_t, BITS_PER_TYPE(int) - 1,
-					      p->tcfp_keys[i].shift);
+		nparms->tcfp_keys[i].shift = min_t(size_t,
+						   BITS_PER_TYPE(int) - 1,
+						   nparms->tcfp_keys[i].shift);
 
 		/* The AT option can read a single byte, we can bound the actual
 		 * value with uchar max.
 		 */
-		cur += (0xff & p->tcfp_keys[i].offmask) >> p->tcfp_keys[i].shift;
+		cur += (0xff & nparms->tcfp_keys[i].offmask) >> nparms->tcfp_keys[i].shift;
 
 		/* Each key touches 4 bytes starting from the computed offset */
-		p->tcfp_off_max_hint = max(p->tcfp_off_max_hint, cur + 4);
+		nparms->tcfp_off_max_hint =
+			max(nparms->tcfp_off_max_hint, cur + 4);
 	}
 
-	p->tcfp_flags = parm->flags;
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 
-	kfree(p->tcfp_keys_ex);
-	p->tcfp_keys_ex = keys_ex;
+	rcu_assign_pointer(p->parms, nparms);
 
 	spin_unlock_bh(&p->tcf_lock);
+
+	if (oparms)
+		call_rcu(&oparms->rcu, tcf_pedit_cleanup_rcu);
+
 	if (goto_ch)
 		tcf_chain_put_by_act(goto_ch);
+
 	return ret;
 
-put_chain:
-	if (goto_ch)
-		tcf_chain_put_by_act(goto_ch);
 out_release:
 	tcf_idr_release(*a, bind);
+out_free_ex:
+	kfree(nparms->tcfp_keys_ex);
 out_free:
-	kfree(keys_ex);
+	kfree(nparms);
 	return ret;
-
 }
 
 static void tcf_pedit_cleanup(struct tc_action *a)
 {
 	struct tcf_pedit *p = to_pedit(a);
-	struct tc_pedit_key *keys = p->tcfp_keys;
+	struct tcf_pedit_parms *parms;
 
-	kfree(keys);
-	kfree(p->tcfp_keys_ex);
+	parms = rcu_dereference_protected(p->parms, 1);
+	call_rcu(&parms->rcu, tcf_pedit_cleanup_rcu);
 }
 
 static bool offset_valid(struct sk_buff *skb, int offset)
@@ -324,109 +352,107 @@ TC_INDIRECT_SCOPE int tcf_pedit_act(struct sk_buff *skb,
 				    const struct tc_action *a,
 				    struct tcf_result *res)
 {
+	enum pedit_header_type htype = TCA_PEDIT_KEY_EX_HDR_TYPE_NETWORK;
+	enum pedit_cmd cmd = TCA_PEDIT_KEY_EX_CMD_SET;
 	struct tcf_pedit *p = to_pedit(a);
+	struct tcf_pedit_key_ex *tkey_ex;
+	struct tcf_pedit_parms *parms;
+	struct tc_pedit_key *tkey;
 	u32 max_offset;
 	int i;
 
-	spin_lock(&p->tcf_lock);
+	parms = rcu_dereference_bh(p->parms);
 
 	max_offset = (skb_transport_header_was_set(skb) ?
 		      skb_transport_offset(skb) :
 		      skb_network_offset(skb)) +
-		     p->tcfp_off_max_hint;
+		     parms->tcfp_off_max_hint;
 	if (skb_ensure_writable(skb, min(skb->len, max_offset)))
-		goto unlock;
+		goto done;
 
 	tcf_lastuse_update(&p->tcf_tm);
+	tcf_action_update_bstats(&p->common, skb);
 
-	if (p->tcfp_nkeys > 0) {
-		struct tc_pedit_key *tkey = p->tcfp_keys;
-		struct tcf_pedit_key_ex *tkey_ex = p->tcfp_keys_ex;
-		enum pedit_header_type htype =
-			TCA_PEDIT_KEY_EX_HDR_TYPE_NETWORK;
-		enum pedit_cmd cmd = TCA_PEDIT_KEY_EX_CMD_SET;
-
-		for (i = p->tcfp_nkeys; i > 0; i--, tkey++) {
-			u32 *ptr, hdata;
-			int offset = tkey->off;
-			int hoffset;
-			u32 val;
-			int rc;
-
-			if (tkey_ex) {
-				htype = tkey_ex->htype;
-				cmd = tkey_ex->cmd;
-
-				tkey_ex++;
-			}
+	tkey_ex = parms->tcfp_keys_ex;
+	tkey = parms->tcfp_keys;
 
-			rc = pedit_skb_hdr_offset(skb, htype, &hoffset);
-			if (rc) {
-				pr_info("tc action pedit bad header type specified (0x%x)\n",
-					htype);
-				goto bad;
-			}
+	for (i = parms->tcfp_nkeys; i > 0; i--, tkey++) {
+		u32 *ptr, hdata;
+		int offset = tkey->off;
+		int hoffset;
+		u32 val;
+		int rc;
 
-			if (tkey->offmask) {
-				u8 *d, _d;
-
-				if (!offset_valid(skb, hoffset + tkey->at)) {
-					pr_info("tc action pedit 'at' offset %d out of bounds\n",
-						hoffset + tkey->at);
-					goto bad;
-				}
-				d = skb_header_pointer(skb, hoffset + tkey->at,
-						       sizeof(_d), &_d);
-				if (!d)
-					goto bad;
-				offset += (*d & tkey->offmask) >> tkey->shift;
-			}
+		if (tkey_ex) {
+			htype = tkey_ex->htype;
+			cmd = tkey_ex->cmd;
 
-			if (offset % 4) {
-				pr_info("tc action pedit offset must be on 32 bit boundaries\n");
-				goto bad;
-			}
+			tkey_ex++;
+		}
 
-			if (!offset_valid(skb, hoffset + offset)) {
-				pr_info("tc action pedit offset %d out of bounds\n",
-					hoffset + offset);
-				goto bad;
-			}
+		rc = pedit_skb_hdr_offset(skb, htype, &hoffset);
+		if (rc) {
+			pr_info("tc action pedit bad header type specified (0x%x)\n",
+				htype);
+			goto bad;
+		}
 
-			ptr = skb_header_pointer(skb, hoffset + offset,
-						 sizeof(hdata), &hdata);
-			if (!ptr)
-				goto bad;
-			/* just do it, baby */
-			switch (cmd) {
-			case TCA_PEDIT_KEY_EX_CMD_SET:
-				val = tkey->val;
-				break;
-			case TCA_PEDIT_KEY_EX_CMD_ADD:
-				val = (*ptr + tkey->val) & ~tkey->mask;
-				break;
-			default:
-				pr_info("tc action pedit bad command (%d)\n",
-					cmd);
+		if (tkey->offmask) {
+			u8 *d, _d;
+
+			if (!offset_valid(skb, hoffset + tkey->at)) {
+				pr_info("tc action pedit 'at' offset %d out of bounds\n",
+					hoffset + tkey->at);
 				goto bad;
 			}
+			d = skb_header_pointer(skb, hoffset + tkey->at,
+					       sizeof(_d), &_d);
+			if (!d)
+				goto bad;
+			offset += (*d & tkey->offmask) >> tkey->shift;
+		}
 
-			*ptr = ((*ptr & tkey->mask) ^ val);
-			if (ptr == &hdata)
-				skb_store_bits(skb, hoffset + offset, ptr, 4);
+		if (offset % 4) {
+			pr_info("tc action pedit offset must be on 32 bit boundaries\n");
+			goto bad;
 		}
 
-		goto done;
-	} else {
-		WARN(1, "pedit BUG: index %d\n", p->tcf_index);
+		if (!offset_valid(skb, hoffset + offset)) {
+			pr_info("tc action pedit offset %d out of bounds\n",
+				hoffset + offset);
+			goto bad;
+		}
+
+		ptr = skb_header_pointer(skb, hoffset + offset,
+					 sizeof(hdata), &hdata);
+		if (!ptr)
+			goto bad;
+		/* just do it, baby */
+		switch (cmd) {
+		case TCA_PEDIT_KEY_EX_CMD_SET:
+			val = tkey->val;
+			break;
+		case TCA_PEDIT_KEY_EX_CMD_ADD:
+			val = (*ptr + tkey->val) & ~tkey->mask;
+			break;
+		default:
+			pr_info("tc action pedit bad command (%d)\n",
+				cmd);
+			goto bad;
+		}
+
+		*ptr = ((*ptr & tkey->mask) ^ val);
+		if (ptr == &hdata)
+			skb_store_bits(skb, hoffset + offset, ptr, 4);
 	}
 
+	goto done;
+
 bad:
+	spin_lock(&p->tcf_lock);
 	p->tcf_qstats.overlimits++;
-done:
-	bstats_update(&p->tcf_bstats, skb);
-unlock:
 	spin_unlock(&p->tcf_lock);
+done:
 	return p->tcf_action;
 }
 
@@ -445,30 +471,33 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct tc_action *a,
 {
 	unsigned char *b = skb_tail_pointer(skb);
 	struct tcf_pedit *p = to_pedit(a);
+	struct tcf_pedit_parms *parms;
 	struct tc_pedit *opt;
 	struct tcf_t t;
 	int s;
 
-	s = struct_size(opt, keys, p->tcfp_nkeys);
+	spin_lock_bh(&p->tcf_lock);
+	parms = rcu_dereference_protected(p->parms, 1);
+	s = struct_size(opt, keys, parms->tcfp_nkeys);
 
-	/* netlink spinlocks held above us - must use ATOMIC */
 	opt = kzalloc(s, GFP_ATOMIC);
-	if (unlikely(!opt))
+	if (unlikely(!opt)) {
+		spin_unlock_bh(&p->tcf_lock);
 		return -ENOBUFS;
+	}
 
-	spin_lock_bh(&p->tcf_lock);
-	memcpy(opt->keys, p->tcfp_keys, flex_array_size(opt, keys, p->tcfp_nkeys));
+	memcpy(opt->keys, parms->tcfp_keys,
+	       flex_array_size(opt, keys, parms->tcfp_nkeys));
 	opt->index = p->tcf_index;
-	opt->nkeys = p->tcfp_nkeys;
-	opt->flags = p->tcfp_flags;
+	opt->nkeys = parms->tcfp_nkeys;
+	opt->flags = parms->tcfp_flags;
 	opt->action = p->tcf_action;
 	opt->refcnt = refcount_read(&p->tcf_refcnt) - ref;
 	opt->bindcnt = atomic_read(&p->tcf_bindcnt) - bind;
 
-	if (p->tcfp_keys_ex) {
-		if (tcf_pedit_key_ex_dump(skb,
-					  p->tcfp_keys_ex,
-					  p->tcfp_nkeys))
+	if (parms->tcfp_keys_ex) {
+		if (tcf_pedit_key_ex_dump(skb, parms->tcfp_keys_ex,
+					  parms->tcfp_nkeys))
 			goto nla_put_failure;
 
 		if (nla_put(skb, TCA_PEDIT_PARMS_EX, s, opt))
-- 
2.34.1

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