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act_police: improved accuracy at high rates
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Current act_police uses rate table computed by the "tc" userspace
program, which has the following issue:

The rate table has 256 entries to map packet lengths to token (time
units).  With TSO sized packets, the 256 entry granularity leads to
loss/gain of rate, making the token bucket inaccurate.

Thus, instead of relying on rate table, this patch explicitly computes
the time and accounts for packet transmission times with nanosecond
granularity.

This is a followup to 56b765b
("htb: improved accuracy at high rates").

Signed-off-by: Jiri Pirko <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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@jpirko @davem330
jpirko authored and davem330 committed Feb 12, 2013
1 parent 0e24321 commit c6d14ff
Showing 1 changed file with 53 additions and 46 deletions.
99 changes: 53 additions & 46 deletions net/sched/act_police.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,20 +26,20 @@ struct tcf_police {
struct tcf_common common;
int tcfp_result;
u32 tcfp_ewma_rate;
u32 tcfp_burst;
s64 tcfp_burst;
u32 tcfp_mtu;
u32 tcfp_toks;
u32 tcfp_ptoks;
psched_time_t tcfp_t_c;
struct qdisc_rate_table *tcfp_R_tab;
struct qdisc_rate_table *tcfp_P_tab;
s64 tcfp_toks;
s64 tcfp_ptoks;
s64 tcfp_mtu_ptoks;
s64 tcfp_t_c;
struct psched_ratecfg rate;
bool rate_present;
struct psched_ratecfg peak;
bool peak_present;
};
#define to_police(pc) \
container_of(pc, struct tcf_police, common)

#define L2T(p, L) qdisc_l2t((p)->tcfp_R_tab, L)
#define L2T_P(p, L) qdisc_l2t((p)->tcfp_P_tab, L)

#define POL_TAB_MASK 15
static struct tcf_common *tcf_police_ht[POL_TAB_MASK + 1];
static u32 police_idx_gen;
Expand Down Expand Up @@ -123,10 +123,6 @@ static void tcf_police_destroy(struct tcf_police *p)
write_unlock_bh(&police_lock);
gen_kill_estimator(&p->tcf_bstats,
&p->tcf_rate_est);
if (p->tcfp_R_tab)
qdisc_put_rtab(p->tcfp_R_tab);
if (p->tcfp_P_tab)
qdisc_put_rtab(p->tcfp_P_tab);
/*
* gen_estimator est_timer() might access p->tcf_lock
* or bstats, wait a RCU grace period before freeing p
Expand Down Expand Up @@ -227,26 +223,36 @@ static int tcf_act_police_locate(struct net *net, struct nlattr *nla,
}

/* No failure allowed after this point */
if (R_tab != NULL) {
qdisc_put_rtab(police->tcfp_R_tab);
police->tcfp_R_tab = R_tab;
police->tcfp_mtu = parm->mtu;
if (police->tcfp_mtu == 0) {
police->tcfp_mtu = ~0;
if (R_tab)
police->tcfp_mtu = 255 << R_tab->rate.cell_log;
}
if (R_tab) {
police->rate_present = true;
psched_ratecfg_precompute(&police->rate, R_tab->rate.rate);
qdisc_put_rtab(R_tab);
} else {
police->rate_present = false;
}
if (P_tab != NULL) {
qdisc_put_rtab(police->tcfp_P_tab);
police->tcfp_P_tab = P_tab;
if (P_tab) {
police->peak_present = true;
psched_ratecfg_precompute(&police->peak, P_tab->rate.rate);
qdisc_put_rtab(P_tab);
} else {
police->peak_present = false;
}

if (tb[TCA_POLICE_RESULT])
police->tcfp_result = nla_get_u32(tb[TCA_POLICE_RESULT]);
police->tcfp_toks = police->tcfp_burst = parm->burst;
police->tcfp_mtu = parm->mtu;
if (police->tcfp_mtu == 0) {
police->tcfp_mtu = ~0;
if (police->tcfp_R_tab)
police->tcfp_mtu = 255<<police->tcfp_R_tab->rate.cell_log;
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;
}
if (police->tcfp_P_tab)
police->tcfp_ptoks = L2T_P(police, police->tcfp_mtu);
police->tcf_action = parm->action;

if (tb[TCA_POLICE_AVRATE])
Expand All @@ -256,7 +262,7 @@ static int tcf_act_police_locate(struct net *net, struct nlattr *nla,
if (ret != ACT_P_CREATED)
return ret;

police->tcfp_t_c = psched_get_time();
police->tcfp_t_c = ktime_to_ns(ktime_get());
police->tcf_index = parm->index ? parm->index :
tcf_hash_new_index(&police_idx_gen, &police_hash_info);
h = tcf_hash(police->tcf_index, POL_TAB_MASK);
Expand Down Expand Up @@ -302,9 +308,9 @@ static int tcf_act_police(struct sk_buff *skb, const struct tc_action *a,
struct tcf_result *res)
{
struct tcf_police *police = a->priv;
psched_time_t now;
long toks;
long ptoks = 0;
s64 now;
s64 toks;
s64 ptoks = 0;

spin_lock(&police->tcf_lock);

Expand All @@ -320,24 +326,25 @@ static int tcf_act_police(struct sk_buff *skb, const struct tc_action *a,
}

if (qdisc_pkt_len(skb) <= police->tcfp_mtu) {
if (police->tcfp_R_tab == NULL) {
if (!police->rate_present) {
spin_unlock(&police->tcf_lock);
return police->tcfp_result;
}

now = psched_get_time();
toks = psched_tdiff_bounded(now, police->tcfp_t_c,
police->tcfp_burst);
if (police->tcfp_P_tab) {
now = ktime_to_ns(ktime_get());
toks = min_t(s64, now - police->tcfp_t_c,
police->tcfp_burst);
if (police->peak_present) {
ptoks = toks + police->tcfp_ptoks;
if (ptoks > (long)L2T_P(police, police->tcfp_mtu))
ptoks = (long)L2T_P(police, police->tcfp_mtu);
ptoks -= L2T_P(police, qdisc_pkt_len(skb));
if (ptoks > police->tcfp_mtu_ptoks)
ptoks = police->tcfp_mtu_ptoks;
ptoks -= (s64) psched_l2t_ns(&police->peak,
qdisc_pkt_len(skb));
}
toks += police->tcfp_toks;
if (toks > (long)police->tcfp_burst)
if (toks > police->tcfp_burst)
toks = police->tcfp_burst;
toks -= L2T(police, qdisc_pkt_len(skb));
toks -= (s64) psched_l2t_ns(&police->rate, qdisc_pkt_len(skb));
if ((toks|ptoks) >= 0) {
police->tcfp_t_c = now;
police->tcfp_toks = toks;
Expand All @@ -363,15 +370,15 @@ tcf_act_police_dump(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
.index = police->tcf_index,
.action = police->tcf_action,
.mtu = police->tcfp_mtu,
.burst = police->tcfp_burst,
.burst = PSCHED_NS2TICKS(police->tcfp_burst),
.refcnt = police->tcf_refcnt - ref,
.bindcnt = police->tcf_bindcnt - bind,
};

if (police->tcfp_R_tab)
opt.rate = police->tcfp_R_tab->rate;
if (police->tcfp_P_tab)
opt.peakrate = police->tcfp_P_tab->rate;
if (police->rate_present)
opt.rate.rate = psched_ratecfg_getrate(&police->rate);
if (police->peak_present)
opt.peakrate.rate = psched_ratecfg_getrate(&police->peak);
if (nla_put(skb, TCA_POLICE_TBF, sizeof(opt), &opt))
goto nla_put_failure;
if (police->tcfp_result &&
Expand Down

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