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Revert: "net: sched: put back q.qlen into a single location"

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This revert commit 46b1c18f9d ("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
e5f0e8f8e4 ("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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2019-04-10 14:32:41 +02:00 committed by David S. Miller
parent 8a53e616de
commit 73eb628ddf
3 changed files with 28 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
include/net/sch_generic.h
View File

@ -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--;

2
net/core/gen_stats.c
View File

@ -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;

9
net/sched/sch_generic.c
View File

@ -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;
}
}