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Date: Wed, 17 Aug 2016 12:36:46 -0700
From: John Fastabend <john.fastabend@...il.com>
To: xiyou.wangcong@...il.com, jhs@...atatu.com,
alexei.starovoitov@...il.com, eric.dumazet@...il.com,
brouer@...hat.com
Cc: john.r.fastabend@...el.com, netdev@...r.kernel.org,
john.fastabend@...il.com, davem@...emloft.net
Subject: [RFC PATCH 08/13] net: sched: support skb_bad_tx with lockless qdisc
Similar to how gso is handled skb_bad_tx needs to be per cpu to handle
lockless qdisc with multiple writer/producers.
Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
---
include/net/sch_generic.h | 7 +++
net/sched/sch_api.c | 6 +++
net/sched/sch_generic.c | 95 +++++++++++++++++++++++++++++++++++++++++----
3 files changed, 99 insertions(+), 9 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 0864813..d465fb9 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -40,6 +40,10 @@ struct gso_cell {
struct sk_buff *skb;
};
+struct bad_txq_cell {
+ struct sk_buff *skb;
+};
+
struct Qdisc {
int (*enqueue)(struct sk_buff *skb,
struct Qdisc *sch,
@@ -77,7 +81,8 @@ struct Qdisc {
struct gnet_stats_basic_cpu __percpu *cpu_bstats;
struct gnet_stats_queue __percpu *cpu_qstats;
- struct gso_cell __percpu *gso_cpu_skb;
+ struct gso_cell __percpu *gso_cpu_skb;
+ struct bad_txq_cell __percpu *skb_bad_txq_cpu;
/*
* For performance sake on SMP, we put highly modified fields at the end
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index d713052..b90a23a 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -970,6 +970,11 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue,
sch->gso_cpu_skb = alloc_percpu(struct gso_cell);
if (!sch->gso_cpu_skb)
goto err_out4;
+
+ sch->skb_bad_txq_cpu =
+ alloc_percpu(struct bad_txq_cell);
+ if (!sch->skb_bad_txq_cpu)
+ goto err_out4;
}
if (tca[TCA_STAB]) {
@@ -1021,6 +1026,7 @@ err_out4:
free_percpu(sch->cpu_bstats);
free_percpu(sch->cpu_qstats);
free_percpu(sch->gso_cpu_skb);
+ free_percpu(sch->skb_bad_txq_cpu);
/*
* Any broken qdiscs that would require a ops->reset() here?
* The qdisc was never in action so it shouldn't be necessary.
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 29238c4..d10b762 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -44,6 +44,43 @@ EXPORT_SYMBOL(default_qdisc_ops);
* - ingress filtering is also serialized via qdisc root lock
* - updates to tree and tree walking are only done under the rtnl mutex.
*/
+static inline struct sk_buff *qdisc_dequeue_skb_bad_txq(struct Qdisc *sch)
+{
+ if (sch->skb_bad_txq_cpu) {
+ struct bad_txq_cell *cell = this_cpu_ptr(sch->skb_bad_txq_cpu);
+
+ return cell->skb;
+ }
+
+ return sch->skb_bad_txq;
+}
+
+static inline void qdisc_enqueue_skb_bad_txq(struct Qdisc *sch,
+ struct sk_buff *skb)
+{
+ if (sch->skb_bad_txq_cpu) {
+ struct bad_txq_cell *cell = this_cpu_ptr(sch->skb_bad_txq_cpu);
+
+ cell->skb = skb;
+ __netif_schedule(sch);
+ return;
+ }
+
+ sch->skb_bad_txq = skb;
+}
+
+static inline void qdisc_null_skb_bad_txq(struct Qdisc *sch)
+{
+ if (sch->skb_bad_txq_cpu) {
+ struct bad_txq_cell *cell = this_cpu_ptr(sch->skb_bad_txq_cpu);
+
+ cell->skb = NULL;
+ return;
+ }
+
+ sch->skb_bad_txq = NULL;
+}
+
static inline struct sk_buff *qdisc_dequeue_gso_skb(struct Qdisc *sch)
{
if (sch->gso_cpu_skb)
@@ -129,9 +166,15 @@ static void try_bulk_dequeue_skb_slow(struct Qdisc *q,
if (!nskb)
break;
if (unlikely(skb_get_queue_mapping(nskb) != mapping)) {
- q->skb_bad_txq = nskb;
- qdisc_qstats_backlog_inc(q, nskb);
- q->q.qlen++;
+ qdisc_enqueue_skb_bad_txq(q, nskb);
+
+ if (qdisc_is_percpu_stats(q)) {
+ qdisc_qstats_cpu_backlog_inc(q, nskb);
+ qdisc_qstats_cpu_qlen_inc(q);
+ } else {
+ qdisc_qstats_backlog_inc(q, nskb);
+ q->q.qlen++;
+ }
break;
}
skb->next = nskb;
@@ -160,7 +203,7 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
qdisc_null_gso_skb(q);
if (qdisc_is_percpu_stats(q)) {
- qdisc_qstats_cpu_backlog_inc(q, skb);
+ qdisc_qstats_cpu_backlog_dec(q, skb);
qdisc_qstats_cpu_qlen_dec(q);
} else {
qdisc_qstats_backlog_dec(q, skb);
@@ -171,14 +214,19 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
return skb;
}
*validate = true;
- skb = q->skb_bad_txq;
+ skb = qdisc_dequeue_skb_bad_txq(q);
if (unlikely(skb)) {
/* check the reason of requeuing without tx lock first */
txq = skb_get_tx_queue(txq->dev, skb);
if (!netif_xmit_frozen_or_stopped(txq)) {
- q->skb_bad_txq = NULL;
- qdisc_qstats_backlog_dec(q, skb);
- q->q.qlen--;
+ qdisc_null_skb_bad_txq(q);
+ if (qdisc_is_percpu_stats(q)) {
+ qdisc_qstats_cpu_backlog_dec(q, skb);
+ qdisc_qstats_cpu_qlen_dec(q);
+ } else {
+ qdisc_qstats_backlog_dec(q, skb);
+ q->q.qlen--;
+ }
goto bulk;
}
return NULL;
@@ -716,6 +764,10 @@ struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
sch->gso_cpu_skb = alloc_percpu(struct gso_cell);
if (!sch->gso_cpu_skb)
goto errout;
+
+ sch->skb_bad_txq_cpu = alloc_percpu(struct bad_txq_cell);
+ if (!sch->skb_bad_txq_cpu)
+ goto errout;
}
return sch;
@@ -746,6 +798,20 @@ void qdisc_reset(struct Qdisc *qdisc)
cell = per_cpu_ptr(qdisc->gso_cpu_skb, i);
if (cell) {
kfree_skb_list(cell->skb);
+ cell->skb = NULL;
+ }
+ }
+ }
+
+ if (qdisc->skb_bad_txq_cpu) {
+ int i;
+
+ for_each_possible_cpu(i) {
+ struct bad_txq_cell *cell;
+
+ cell = per_cpu_ptr(qdisc->skb_bad_txq_cpu, i);
+ if (cell) {
+ kfree_skb(cell->skb);
cell = NULL;
}
}
@@ -781,6 +847,19 @@ static void qdisc_rcu_free(struct rcu_head *head)
free_percpu(qdisc->gso_cpu_skb);
}
+ if (qdisc->skb_bad_txq_cpu) {
+ int i;
+
+ for_each_possible_cpu(i) {
+ struct bad_txq_cell *cell;
+
+ cell = per_cpu_ptr(qdisc->skb_bad_txq_cpu, i);
+ kfree_skb(cell->skb);
+ }
+
+ free_percpu(qdisc->skb_bad_txq_cpu);
+ }
+
kfree((char *) qdisc - qdisc->padded);
}
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