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Message-Id: <6d287f706fdcff76eb1e9a1c85ea6ce188db11d8.1536852493.git.dcaratti@redhat.com>
Date: Thu, 13 Sep 2018 19:29:13 +0200
From: Davide Caratti <dcaratti@...hat.com>
To: Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>,
"David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org
Subject: [PATCH net-next 2/2] net/sched: act_police: don't use spinlock in the data path
use RCU instead of spinlocks, to protect concurrent read/write on
act_police configuration. This reduces the effects of contention in the
data path, in case multiple readers are present.
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
net/sched/act_police.c | 156 ++++++++++++++++++++++++-----------------
1 file changed, 92 insertions(+), 64 deletions(-)
diff --git a/net/sched/act_police.c b/net/sched/act_police.c
index 965a48d3ec35..92649d2667ed 100644
--- a/net/sched/act_police.c
+++ b/net/sched/act_police.c
@@ -22,8 +22,7 @@
#include <net/act_api.h>
#include <net/netlink.h>
-struct tcf_police {
- struct tc_action common;
+struct tcf_police_params {
int tcfp_result;
u32 tcfp_ewma_rate;
s64 tcfp_burst;
@@ -36,6 +35,12 @@ struct tcf_police {
bool rate_present;
struct psched_ratecfg peak;
bool peak_present;
+ struct rcu_head rcu;
+};
+
+struct tcf_police {
+ struct tc_action common;
+ struct tcf_police_params __rcu *params;
};
#define to_police(pc) ((struct tcf_police *)pc)
@@ -84,6 +89,7 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
struct tcf_police *police;
struct qdisc_rate_table *R_tab = NULL, *P_tab = NULL;
struct tc_action_net *tn = net_generic(net, police_net_id);
+ struct tcf_police_params *new;
bool exists = false;
int size;
@@ -151,50 +157,60 @@ static int tcf_police_init(struct net *net, struct nlattr *nla,
goto failure;
}
- spin_lock_bh(&police->tcf_lock);
+ new = kzalloc(sizeof(*new), GFP_KERNEL);
+ if (unlikely(!new)) {
+ err = -ENOMEM;
+ goto failure;
+ }
+
/* No failure allowed after this point */
- police->tcfp_mtu = parm->mtu;
- if (police->tcfp_mtu == 0) {
- police->tcfp_mtu = ~0;
+ new->tcfp_mtu = parm->mtu;
+ if (!new->tcfp_mtu) {
+ new->tcfp_mtu = ~0;
if (R_tab)
- police->tcfp_mtu = 255 << R_tab->rate.cell_log;
+ new->tcfp_mtu = 255 << R_tab->rate.cell_log;
}
if (R_tab) {
- police->rate_present = true;
- psched_ratecfg_precompute(&police->rate, &R_tab->rate, 0);
+ new->rate_present = true;
+ psched_ratecfg_precompute(&new->rate, &R_tab->rate, 0);
qdisc_put_rtab(R_tab);
} else {
- police->rate_present = false;
+ new->rate_present = false;
}
if (P_tab) {
- police->peak_present = true;
- psched_ratecfg_precompute(&police->peak, &P_tab->rate, 0);
+ new->peak_present = true;
+ psched_ratecfg_precompute(&new->peak, &P_tab->rate, 0);
qdisc_put_rtab(P_tab);
} else {
- police->peak_present = false;
+ new->peak_present = false;
}
if (tb[TCA_POLICE_RESULT])
- police->tcfp_result = nla_get_u32(tb[TCA_POLICE_RESULT]);
- police->tcfp_burst = PSCHED_TICKS2NS(parm->burst);
- police->tcfp_toks = police->tcfp_burst;
- if (police->peak_present) {
- police->tcfp_mtu_ptoks = (s64) psched_l2t_ns(&police->peak,
- police->tcfp_mtu);
- police->tcfp_ptoks = police->tcfp_mtu_ptoks;
+ new->tcfp_result = nla_get_u32(tb[TCA_POLICE_RESULT]);
+ new->tcfp_burst = PSCHED_TICKS2NS(parm->burst);
+ new->tcfp_toks = new->tcfp_burst;
+ if (new->peak_present) {
+ new->tcfp_mtu_ptoks = (s64)psched_l2t_ns(&new->peak,
+ new->tcfp_mtu);
+ new->tcfp_ptoks = new->tcfp_mtu_ptoks;
}
- police->tcf_action = parm->action;
if (tb[TCA_POLICE_AVRATE])
- police->tcfp_ewma_rate = nla_get_u32(tb[TCA_POLICE_AVRATE]);
+ new->tcfp_ewma_rate = nla_get_u32(tb[TCA_POLICE_AVRATE]);
+ spin_lock_bh(&police->tcf_lock);
+ new->tcfp_t_c = ktime_get_ns();
+ police->tcf_action = parm->action;
+ rcu_swap_protected(police->params,
+ new,
+ lockdep_is_held(&police->tcf_lock));
spin_unlock_bh(&police->tcf_lock);
- if (ret != ACT_P_CREATED)
- return ret;
- police->tcfp_t_c = ktime_get_ns();
- tcf_idr_insert(tn, *a);
+ if (new)
+ kfree_rcu(new, rcu);
+ if (ret == ACT_P_CREATED)
+ tcf_idr_insert(tn, *a);
return ret;
failure:
@@ -208,68 +224,77 @@ static int tcf_police_act(struct sk_buff *skb, const struct tc_action *a,
struct tcf_result *res)
{
struct tcf_police *police = to_police(a);
+ struct tcf_police_params *p;
s64 now, toks, ptoks = 0;
int ret;
tcf_lastuse_update(&police->tcf_tm);
bstats_cpu_update(this_cpu_ptr(police->common.cpu_bstats), skb);
- spin_lock(&police->tcf_lock);
- if (police->tcfp_ewma_rate) {
+ ret = READ_ONCE(police->tcf_action);
+ p = rcu_dereference_bh(police->params);
+
+ if (p->tcfp_ewma_rate) {
struct gnet_stats_rate_est64 sample;
if (!gen_estimator_read(&police->tcf_rate_est, &sample) ||
- sample.bps >= police->tcfp_ewma_rate) {
- ret = police->tcf_action;
+ sample.bps >= p->tcfp_ewma_rate)
goto inc_overlimits;
- }
}
- if (qdisc_pkt_len(skb) <= police->tcfp_mtu) {
- if (!police->rate_present) {
- ret = police->tcfp_result;
- goto unlock;
+ if (qdisc_pkt_len(skb) <= p->tcfp_mtu) {
+ if (!p->rate_present) {
+ ret = p->tcfp_result;
+ goto end;
}
now = ktime_get_ns();
- toks = min_t(s64, now - police->tcfp_t_c,
- police->tcfp_burst);
- if (police->peak_present) {
- ptoks = toks + police->tcfp_ptoks;
- if (ptoks > police->tcfp_mtu_ptoks)
- ptoks = police->tcfp_mtu_ptoks;
- ptoks -= (s64) psched_l2t_ns(&police->peak,
- qdisc_pkt_len(skb));
+ toks = min_t(s64, now - p->tcfp_t_c, p->tcfp_burst);
+ if (p->peak_present) {
+ ptoks = toks + p->tcfp_ptoks;
+ if (ptoks > p->tcfp_mtu_ptoks)
+ ptoks = p->tcfp_mtu_ptoks;
+ ptoks -= (s64)psched_l2t_ns(&p->peak,
+ qdisc_pkt_len(skb));
}
- toks += police->tcfp_toks;
- if (toks > police->tcfp_burst)
- toks = police->tcfp_burst;
- toks -= (s64) psched_l2t_ns(&police->rate, qdisc_pkt_len(skb));
+ toks += p->tcfp_toks;
+ if (toks > p->tcfp_burst)
+ toks = p->tcfp_burst;
+ toks -= (s64)psched_l2t_ns(&p->rate, qdisc_pkt_len(skb));
if ((toks|ptoks) >= 0) {
- police->tcfp_t_c = now;
- police->tcfp_toks = toks;
- police->tcfp_ptoks = ptoks;
- ret = police->tcfp_result;
+ p->tcfp_t_c = now;
+ p->tcfp_toks = toks;
+ p->tcfp_ptoks = ptoks;
+ ret = p->tcfp_result;
goto inc_drops;
}
}
- ret = police->tcf_action;
inc_overlimits:
qstats_overlimit_inc(this_cpu_ptr(police->common.cpu_qstats));
inc_drops:
if (ret == TC_ACT_SHOT)
qstats_drop_inc(this_cpu_ptr(police->common.cpu_qstats));
-unlock:
- spin_unlock(&police->tcf_lock);
+end:
return ret;
}
+static void tcf_police_cleanup(struct tc_action *a)
+{
+ struct tcf_police *police = to_police(a);
+ struct tcf_police_params *p;
+
+ p = rcu_dereference_protected(police->params, 1);
+ if (p)
+ kfree_rcu(p, rcu);
+}
+
static int tcf_police_dump(struct sk_buff *skb, struct tc_action *a,
int bind, int ref)
{
unsigned char *b = skb_tail_pointer(skb);
struct tcf_police *police = to_police(a);
+ struct tcf_police_params *p;
struct tc_police opt = {
.index = police->tcf_index,
.refcnt = refcount_read(&police->tcf_refcnt) - ref,
@@ -279,19 +304,21 @@ static int tcf_police_dump(struct sk_buff *skb, struct tc_action *a,
spin_lock_bh(&police->tcf_lock);
opt.action = police->tcf_action;
- opt.mtu = police->tcfp_mtu;
- opt.burst = PSCHED_NS2TICKS(police->tcfp_burst);
- if (police->rate_present)
- psched_ratecfg_getrate(&opt.rate, &police->rate);
- if (police->peak_present)
- psched_ratecfg_getrate(&opt.peakrate, &police->peak);
+ p = rcu_dereference_protected(police->params,
+ lockdep_is_held(&police->tcf_lock));
+ opt.mtu = p->tcfp_mtu;
+ opt.burst = PSCHED_NS2TICKS(p->tcfp_burst);
+ if (p->rate_present)
+ psched_ratecfg_getrate(&opt.rate, &p->rate);
+ if (p->peak_present)
+ psched_ratecfg_getrate(&opt.peakrate, &p->peak);
if (nla_put(skb, TCA_POLICE_TBF, sizeof(opt), &opt))
goto nla_put_failure;
- if (police->tcfp_result &&
- nla_put_u32(skb, TCA_POLICE_RESULT, police->tcfp_result))
+ if (p->tcfp_result &&
+ nla_put_u32(skb, TCA_POLICE_RESULT, p->tcfp_result))
goto nla_put_failure;
- if (police->tcfp_ewma_rate &&
- nla_put_u32(skb, TCA_POLICE_AVRATE, police->tcfp_ewma_rate))
+ if (p->tcfp_ewma_rate &&
+ nla_put_u32(skb, TCA_POLICE_AVRATE, p->tcfp_ewma_rate))
goto nla_put_failure;
t.install = jiffies_to_clock_t(jiffies - police->tcf_tm.install);
@@ -330,6 +357,7 @@ static struct tc_action_ops act_police_ops = {
.init = tcf_police_init,
.walk = tcf_police_walker,
.lookup = tcf_police_search,
+ .cleanup = tcf_police_cleanup,
.size = sizeof(struct tcf_police),
};
--
2.17.1
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