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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
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--;