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Message-Id: <b3a2f5a5d9e95547c8dcde2a6a921db48fbc88a5.1554892007.git.pabeni@redhat.com>
Date: Wed, 10 Apr 2019 14:32:41 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>,
Eric Dumazet <edumazet@...gle.com>,
Ivan Vecera <ivecera@...hat.com>
Subject: [PATCH net-next v2 5/5] Revert: "net: sched: put back q.qlen into a single location"
This revert commit 46b1c18f9deb ("net: sched: put back q.qlen into
a single location").
After the previous patch, when a NOLOCK qdisc is enslaved to a
locking qdisc it switches to global stats accounting. As a consequence,
when a classful qdisc accesses directly a child qdisc's qlen, such
qdisc is not doing per CPU accounting and qlen value is consistent.
In the control path nobody uses directly qlen since commit
e5f0e8f8e45 ("net: sched: introduce and use qdisc tree flush/purge
helpers"), so we can remove the contented atomic ops from the
datapath.
v1 -> v2:
- complete the qdisc_qstats_atomic_qlen_dec() ->
qdisc_qstats_cpu_qlen_dec() replacement, fix build issue
- more descriptive commit message
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
include/net/sch_generic.h | 37 +++++++++++++++++++++----------------
net/core/gen_stats.c | 2 ++
net/sched/sch_generic.c | 9 +++++----
3 files changed, 28 insertions(+), 20 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index f069011524ba..e8f85cd2afce 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -52,10 +52,7 @@ struct qdisc_size_table {
struct qdisc_skb_head {
struct sk_buff *head;
struct sk_buff *tail;
- union {
- u32 qlen;
- atomic_t atomic_qlen;
- };
+ __u32 qlen;
spinlock_t lock;
};
@@ -486,19 +483,27 @@ static inline void qdisc_cb_private_validate(const struct sk_buff *skb, int sz)
BUILD_BUG_ON(sizeof(qcb->data) < sz);
}
+static inline int qdisc_qlen_cpu(const struct Qdisc *q)
+{
+ return this_cpu_ptr(q->cpu_qstats)->qlen;
+}
+
static inline int qdisc_qlen(const struct Qdisc *q)
{
return q->q.qlen;
}
-static inline u32 qdisc_qlen_sum(const struct Qdisc *q)
+static inline int qdisc_qlen_sum(const struct Qdisc *q)
{
- u32 qlen = q->qstats.qlen;
+ __u32 qlen = q->qstats.qlen;
+ int i;
- if (qdisc_is_percpu_stats(q))
- qlen += atomic_read(&q->q.atomic_qlen);
- else
+ if (qdisc_is_percpu_stats(q)) {
+ for_each_possible_cpu(i)
+ qlen += per_cpu_ptr(q->cpu_qstats, i)->qlen;
+ } else {
qlen += q->q.qlen;
+ }
return qlen;
}
@@ -889,14 +894,14 @@ static inline void qdisc_qstats_cpu_backlog_inc(struct Qdisc *sch,
this_cpu_add(sch->cpu_qstats->backlog, qdisc_pkt_len(skb));
}
-static inline void qdisc_qstats_atomic_qlen_inc(struct Qdisc *sch)
+static inline void qdisc_qstats_cpu_qlen_inc(struct Qdisc *sch)
{
- atomic_inc(&sch->q.atomic_qlen);
+ this_cpu_inc(sch->cpu_qstats->qlen);
}
-static inline void qdisc_qstats_atomic_qlen_dec(struct Qdisc *sch)
+static inline void qdisc_qstats_cpu_qlen_dec(struct Qdisc *sch)
{
- atomic_dec(&sch->q.atomic_qlen);
+ this_cpu_dec(sch->cpu_qstats->qlen);
}
static inline void qdisc_qstats_cpu_requeues_inc(struct Qdisc *sch)
@@ -1112,7 +1117,7 @@ static inline void qdisc_update_stats_at_dequeue(struct Qdisc *sch,
if (qdisc_is_percpu_stats(sch)) {
qdisc_qstats_cpu_backlog_dec(sch, skb);
qdisc_bstats_cpu_update(sch, skb);
- qdisc_qstats_atomic_qlen_dec(sch);
+ qdisc_qstats_cpu_qlen_dec(sch);
} else {
qdisc_qstats_backlog_dec(sch, skb);
qdisc_bstats_update(sch, skb);
@@ -1124,7 +1129,7 @@ static inline void qdisc_update_stats_at_enqueue(struct Qdisc *sch,
unsigned int pkt_len)
{
if (qdisc_is_percpu_stats(sch)) {
- qdisc_qstats_atomic_qlen_inc(sch);
+ qdisc_qstats_cpu_qlen_inc(sch);
this_cpu_add(sch->cpu_qstats->backlog, pkt_len);
} else {
sch->qstats.backlog += pkt_len;
@@ -1141,7 +1146,7 @@ static inline struct sk_buff *qdisc_dequeue_peeked(struct Qdisc *sch)
skb = __skb_dequeue(&sch->gso_skb);
if (qdisc_is_percpu_stats(sch)) {
qdisc_qstats_cpu_backlog_dec(sch, skb);
- qdisc_qstats_atomic_qlen_dec(sch);
+ qdisc_qstats_cpu_qlen_dec(sch);
} else {
qdisc_qstats_backlog_dec(sch, skb);
sch->q.qlen--;
diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index ac679f74ba47..9bf1b9ad1780 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -291,6 +291,7 @@ __gnet_stats_copy_queue_cpu(struct gnet_stats_queue *qstats,
for_each_possible_cpu(i) {
const struct gnet_stats_queue *qcpu = per_cpu_ptr(q, i);
+ qstats->qlen = 0;
qstats->backlog += qcpu->backlog;
qstats->drops += qcpu->drops;
qstats->requeues += qcpu->requeues;
@@ -306,6 +307,7 @@ void __gnet_stats_copy_queue(struct gnet_stats_queue *qstats,
if (cpu) {
__gnet_stats_copy_queue_cpu(qstats, cpu);
} else {
+ qstats->qlen = q->qlen;
qstats->backlog = q->backlog;
qstats->drops = q->drops;
qstats->requeues = q->requeues;
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 12a6e1a39fa0..848aab3693bd 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -68,7 +68,7 @@ static inline struct sk_buff *__skb_dequeue_bad_txq(struct Qdisc *q)
skb = __skb_dequeue(&q->skb_bad_txq);
if (qdisc_is_percpu_stats(q)) {
qdisc_qstats_cpu_backlog_dec(q, skb);
- qdisc_qstats_atomic_qlen_dec(q);
+ qdisc_qstats_cpu_qlen_dec(q);
} else {
qdisc_qstats_backlog_dec(q, skb);
q->q.qlen--;
@@ -108,7 +108,7 @@ static inline void qdisc_enqueue_skb_bad_txq(struct Qdisc *q,
if (qdisc_is_percpu_stats(q)) {
qdisc_qstats_cpu_backlog_inc(q, skb);
- qdisc_qstats_atomic_qlen_inc(q);
+ qdisc_qstats_cpu_qlen_inc(q);
} else {
qdisc_qstats_backlog_inc(q, skb);
q->q.qlen++;
@@ -136,7 +136,7 @@ static inline void dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
if (qdisc_is_percpu_stats(q)) {
qdisc_qstats_cpu_requeues_inc(q);
qdisc_qstats_cpu_backlog_inc(q, skb);
- qdisc_qstats_atomic_qlen_inc(q);
+ qdisc_qstats_cpu_qlen_inc(q);
} else {
q->qstats.requeues++;
qdisc_qstats_backlog_inc(q, skb);
@@ -236,7 +236,7 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
skb = __skb_dequeue(&q->gso_skb);
if (qdisc_is_percpu_stats(q)) {
qdisc_qstats_cpu_backlog_dec(q, skb);
- qdisc_qstats_atomic_qlen_dec(q);
+ qdisc_qstats_cpu_qlen_dec(q);
} else {
qdisc_qstats_backlog_dec(q, skb);
q->q.qlen--;
@@ -694,6 +694,7 @@ static void pfifo_fast_reset(struct Qdisc *qdisc)
struct gnet_stats_queue *q = per_cpu_ptr(qdisc->cpu_qstats, i);
q->backlog = 0;
+ q->qlen = 0;
}
}
--
2.20.1
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