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net/sched: act_police: don't use spinlock in the data path
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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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Davide Caratti authored and David S. Miller committed Sep 16, 2018
1 parent 93be42f commit 2d550db
Showing 1 changed file with 92 additions and 64 deletions.
156 changes: 92 additions & 64 deletions net/sched/act_police.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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)
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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:
Expand All @@ -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,
Expand All @@ -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);
Expand Down Expand Up @@ -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),
};

Expand Down

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