net: sched: do not acquire qdisc spinlock in qdisc/class stats dump
Large tc dumps (tc -s {qdisc|class} sh dev ethX) done by Google BwE host
agent [1] are problematic at scale :
For each qdisc/class found in the dump, we currently lock the root qdisc
spinlock in order to get stats. Sampling stats every 5 seconds from
thousands of HTB classes is a challenge when the root qdisc spinlock is
under high pressure. Not only the dumps take time, they also slow
down the fast path (queue/dequeue packets) by 10 % to 20 % in some cases.
An audit of existing qdiscs showed that sch_fq_codel is the only qdisc
that might need the qdisc lock in fq_codel_dump_stats() and
fq_codel_dump_class_stats()
In v2 of this patch, I now use the Qdisc running seqcount to provide
consistent reads of packets/bytes counters, regardless of 32/64 bit arches.
I also changed rate estimators to use the same infrastructure
so that they no longer need to lock root qdisc lock.
[1]
http://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43838.pdf
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Kevin Athey <kda@google.com>
Cc: Xiaotian Pei <xiaotian@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 719bc2e..b6db56e 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -287,7 +287,7 @@
if (est) {
err = gen_new_estimator(&p->tcfc_bstats, p->cpu_bstats,
&p->tcfc_rate_est,
- &p->tcfc_lock, est);
+ &p->tcfc_lock, NULL, est);
if (err) {
free_percpu(p->cpu_qstats);
goto err2;
@@ -671,7 +671,7 @@
if (err < 0)
goto errout;
- if (gnet_stats_copy_basic(&d, p->cpu_bstats, &p->tcfc_bstats) < 0 ||
+ if (gnet_stats_copy_basic(NULL, &d, p->cpu_bstats, &p->tcfc_bstats) < 0 ||
gnet_stats_copy_rate_est(&d, &p->tcfc_bstats,
&p->tcfc_rate_est) < 0 ||
gnet_stats_copy_queue(&d, p->cpu_qstats,
diff --git a/net/sched/act_police.c b/net/sched/act_police.c
index 820b116..bcb3114 100644
--- a/net/sched/act_police.c
+++ b/net/sched/act_police.c
@@ -185,7 +185,8 @@
if (est) {
err = gen_replace_estimator(&police->tcf_bstats, NULL,
&police->tcf_rate_est,
- &police->tcf_lock, est);
+ &police->tcf_lock,
+ NULL, est);
if (err)
goto failure_unlock;
} else if (tb[TCA_POLICE_AVRATE] &&
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index ddf047d..d4a8bbf 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -982,7 +982,7 @@
rcu_assign_pointer(sch->stab, stab);
}
if (tca[TCA_RATE]) {
- spinlock_t *root_lock;
+ seqcount_t *running;
err = -EOPNOTSUPP;
if (sch->flags & TCQ_F_MQROOT)
@@ -991,14 +991,15 @@
if ((sch->parent != TC_H_ROOT) &&
!(sch->flags & TCQ_F_INGRESS) &&
(!p || !(p->flags & TCQ_F_MQROOT)))
- root_lock = qdisc_root_sleeping_lock(sch);
+ running = qdisc_root_sleeping_running(sch);
else
- root_lock = qdisc_lock(sch);
+ running = &sch->running;
err = gen_new_estimator(&sch->bstats,
sch->cpu_bstats,
&sch->rate_est,
- root_lock,
+ NULL,
+ running,
tca[TCA_RATE]);
if (err)
goto err_out4;
@@ -1061,7 +1062,8 @@
gen_replace_estimator(&sch->bstats,
sch->cpu_bstats,
&sch->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
}
out:
@@ -1369,8 +1371,7 @@
goto nla_put_failure;
if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS, TCA_XSTATS,
- qdisc_root_sleeping_lock(q), &d,
- TCA_PAD) < 0)
+ NULL, &d, TCA_PAD) < 0)
goto nla_put_failure;
if (q->ops->dump_stats && q->ops->dump_stats(q, &d) < 0)
@@ -1381,7 +1382,8 @@
cpu_qstats = q->cpu_qstats;
}
- if (gnet_stats_copy_basic(&d, cpu_bstats, &q->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(q),
+ &d, cpu_bstats, &q->bstats) < 0 ||
gnet_stats_copy_rate_est(&d, &q->bstats, &q->rate_est) < 0 ||
gnet_stats_copy_queue(&d, cpu_qstats, &q->qstats, qlen) < 0)
goto nla_put_failure;
@@ -1684,8 +1686,7 @@
goto nla_put_failure;
if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS, TCA_XSTATS,
- qdisc_root_sleeping_lock(q), &d,
- TCA_PAD) < 0)
+ NULL, &d, TCA_PAD) < 0)
goto nla_put_failure;
if (cl_ops->dump_stats && cl_ops->dump_stats(q, cl, &d) < 0)
diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index 1911af3..34f8f79 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -637,7 +637,8 @@
{
struct atm_flow_data *flow = (struct atm_flow_data *)arg;
- if (gnet_stats_copy_basic(d, NULL, &flow->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &flow->bstats) < 0 ||
gnet_stats_copy_queue(d, NULL, &flow->qstats, flow->q->q.qlen) < 0)
return -1;
diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index baafddf..1b8128f 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -1600,7 +1600,8 @@
if (cl->undertime != PSCHED_PASTPERFECT)
cl->xstats.undertime = cl->undertime - q->now;
- if (gnet_stats_copy_basic(d, NULL, &cl->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &cl->bstats) < 0 ||
gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
gnet_stats_copy_queue(d, NULL, &cl->qstats, cl->q->q.qlen) < 0)
return -1;
@@ -1755,7 +1756,8 @@
if (tca[TCA_RATE]) {
err = gen_replace_estimator(&cl->bstats, NULL,
&cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err) {
qdisc_put_rtab(rtab);
@@ -1848,7 +1850,8 @@
if (tca[TCA_RATE]) {
err = gen_new_estimator(&cl->bstats, NULL, &cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err) {
kfree(cl);
diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index a63e879..1b7e1a2 100644
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -91,7 +91,8 @@
if (tca[TCA_RATE]) {
err = gen_replace_estimator(&cl->bstats, NULL,
&cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err)
return err;
@@ -119,7 +120,8 @@
if (tca[TCA_RATE]) {
err = gen_replace_estimator(&cl->bstats, NULL, &cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err) {
qdisc_destroy(cl->qdisc);
@@ -279,7 +281,8 @@
if (qlen)
xstats.deficit = cl->deficit;
- if (gnet_stats_copy_basic(d, NULL, &cl->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &cl->bstats) < 0 ||
gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
gnet_stats_copy_queue(d, NULL, &cl->qdisc->qstats, qlen) < 0)
return -1;
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index 6883a89..1daa542 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -566,11 +566,13 @@
st.qdisc_stats.memory_usage = q->memory_usage;
st.qdisc_stats.drop_overmemory = q->drop_overmemory;
+ sch_tree_lock(sch);
list_for_each(pos, &q->new_flows)
st.qdisc_stats.new_flows_len++;
list_for_each(pos, &q->old_flows)
st.qdisc_stats.old_flows_len++;
+ sch_tree_unlock(sch);
return gnet_stats_copy_app(d, &st, sizeof(st));
}
@@ -624,7 +626,7 @@
if (idx < q->flows_cnt) {
const struct fq_codel_flow *flow = &q->flows[idx];
- const struct sk_buff *skb = flow->head;
+ const struct sk_buff *skb;
memset(&xstats, 0, sizeof(xstats));
xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
@@ -642,9 +644,14 @@
codel_time_to_us(delta) :
-codel_time_to_us(-delta);
}
- while (skb) {
- qs.qlen++;
- skb = skb->next;
+ if (flow->head) {
+ sch_tree_lock(sch);
+ skb = flow->head;
+ while (skb) {
+ qs.qlen++;
+ skb = skb->next;
+ }
+ sch_tree_unlock(sch);
}
qs.backlog = q->backlogs[idx];
qs.drops = flow->dropped;
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index d783d7c..74813dd 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1015,11 +1015,10 @@
cur_time = psched_get_time();
if (tca[TCA_RATE]) {
- spinlock_t *lock = qdisc_root_sleeping_lock(sch);
-
err = gen_replace_estimator(&cl->bstats, NULL,
&cl->rate_est,
- lock,
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err)
return err;
@@ -1068,7 +1067,8 @@
if (tca[TCA_RATE]) {
err = gen_new_estimator(&cl->bstats, NULL, &cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err) {
kfree(cl);
@@ -1373,7 +1373,7 @@
xstats.work = cl->cl_total;
xstats.rtwork = cl->cl_cumul;
- if (gnet_stats_copy_basic(d, NULL, &cl->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch), d, NULL, &cl->bstats) < 0 ||
gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
gnet_stats_copy_queue(d, NULL, &cl->qstats, cl->qdisc->q.qlen) < 0)
return -1;
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index d4b4218..2b05764 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1141,7 +1141,8 @@
cl->xstats.tokens = PSCHED_NS2TICKS(cl->tokens);
cl->xstats.ctokens = PSCHED_NS2TICKS(cl->ctokens);
- if (gnet_stats_copy_basic(d, NULL, &cl->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &cl->bstats) < 0 ||
gnet_stats_copy_rate_est(d, NULL, &cl->rate_est) < 0 ||
gnet_stats_copy_queue(d, NULL, &cl->qstats, qlen) < 0)
return -1;
@@ -1395,7 +1396,8 @@
if (htb_rate_est || tca[TCA_RATE]) {
err = gen_new_estimator(&cl->bstats, NULL,
&cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE] ? : &est.nla);
if (err) {
kfree(cl);
@@ -1457,11 +1459,10 @@
parent->children++;
} else {
if (tca[TCA_RATE]) {
- spinlock_t *lock = qdisc_root_sleeping_lock(sch);
-
err = gen_replace_estimator(&cl->bstats, NULL,
&cl->rate_est,
- lock,
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err)
return err;
diff --git a/net/sched/sch_mq.c b/net/sched/sch_mq.c
index 56a77b8..b943982 100644
--- a/net/sched/sch_mq.c
+++ b/net/sched/sch_mq.c
@@ -199,7 +199,7 @@
struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
sch = dev_queue->qdisc_sleeping;
- if (gnet_stats_copy_basic(d, NULL, &sch->bstats) < 0 ||
+ if (gnet_stats_copy_basic(&sch->running, d, NULL, &sch->bstats) < 0 ||
gnet_stats_copy_queue(d, NULL, &sch->qstats, sch->q.qlen) < 0)
return -1;
return 0;
diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
index b8002ce..549c663 100644
--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -342,7 +342,8 @@
* hold here is the look on dev_queue->qdisc_sleeping
* also acquired below.
*/
- spin_unlock_bh(d->lock);
+ if (d->lock)
+ spin_unlock_bh(d->lock);
for (i = tc.offset; i < tc.offset + tc.count; i++) {
struct netdev_queue *q = netdev_get_tx_queue(dev, i);
@@ -359,15 +360,17 @@
spin_unlock_bh(qdisc_lock(qdisc));
}
/* Reclaim root sleeping lock before completing stats */
- spin_lock_bh(d->lock);
- if (gnet_stats_copy_basic(d, NULL, &bstats) < 0 ||
+ if (d->lock)
+ spin_lock_bh(d->lock);
+ if (gnet_stats_copy_basic(NULL, d, NULL, &bstats) < 0 ||
gnet_stats_copy_queue(d, NULL, &qstats, qlen) < 0)
return -1;
} else {
struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
sch = dev_queue->qdisc_sleeping;
- if (gnet_stats_copy_basic(d, NULL, &sch->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &sch->bstats) < 0 ||
gnet_stats_copy_queue(d, NULL,
&sch->qstats, sch->q.qlen) < 0)
return -1;
diff --git a/net/sched/sch_multiq.c b/net/sched/sch_multiq.c
index bcdd54bb..21e69d2 100644
--- a/net/sched/sch_multiq.c
+++ b/net/sched/sch_multiq.c
@@ -356,7 +356,8 @@
struct Qdisc *cl_q;
cl_q = q->queues[cl - 1];
- if (gnet_stats_copy_basic(d, NULL, &cl_q->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &cl_q->bstats) < 0 ||
gnet_stats_copy_queue(d, NULL, &cl_q->qstats, cl_q->q.qlen) < 0)
return -1;
diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index fee1b15..06eca70 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -319,7 +319,8 @@
struct Qdisc *cl_q;
cl_q = q->queues[cl - 1];
- if (gnet_stats_copy_basic(d, NULL, &cl_q->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &cl_q->bstats) < 0 ||
gnet_stats_copy_queue(d, NULL, &cl_q->qstats, cl_q->q.qlen) < 0)
return -1;
diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c
index 8d2d8d9..85d4197 100644
--- a/net/sched/sch_qfq.c
+++ b/net/sched/sch_qfq.c
@@ -460,7 +460,8 @@
if (tca[TCA_RATE]) {
err = gen_replace_estimator(&cl->bstats, NULL,
&cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err)
return err;
@@ -486,7 +487,8 @@
if (tca[TCA_RATE]) {
err = gen_new_estimator(&cl->bstats, NULL,
&cl->rate_est,
- qdisc_root_sleeping_lock(sch),
+ NULL,
+ qdisc_root_sleeping_running(sch),
tca[TCA_RATE]);
if (err)
goto destroy_class;
@@ -663,7 +665,8 @@
xstats.weight = cl->agg->class_weight;
xstats.lmax = cl->agg->lmax;
- if (gnet_stats_copy_basic(d, NULL, &cl->bstats) < 0 ||
+ if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+ d, NULL, &cl->bstats) < 0 ||
gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
gnet_stats_copy_queue(d, NULL,
&cl->qdisc->qstats, cl->qdisc->q.qlen) < 0)
