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Commit 4b9c7768 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'sched-refactor-NOLOCK-qdiscs' 



Paolo Abeni says:

====================
sched: refactor NOLOCK qdiscs

With the introduction of NOLOCK qdiscs, pfifo_fast performances in the
uncontended scenario degraded measurably, especially after the commit
eb82a994 ("net: sched, fix OOO packets with pfifo_fast").

This series restore the pfifo_fast performances in such scenario back the
previous level, mainly reducing the number of atomic operations required to
perform the qdisc_run() call. Even performances in the contended scenario
increase measurably.

Note: This series is on top of:

sched: manipulate __QDISC_STATE_RUNNING in qdisc_run_* helpers
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents b9f672af 021a17ed

include/linux/skb_array.h

+5 −0
Original line number Diff line number Diff line
@@ -97,6 +97,11 @@ static inline bool skb_array_empty_any(struct skb_array *a) 
	return ptr_ring_empty_any(&a->ring);

}



static inline struct sk_buff *__skb_array_consume(struct skb_array *a)

{

	return __ptr_ring_consume(&a->ring);

}



static inline struct sk_buff *skb_array_consume(struct skb_array *a)

{

	return ptr_ring_consume(&a->ring);

include/net/sch_generic.h

+5 −5
Original line number Diff line number Diff line
@@ -30,7 +30,6 @@ struct qdisc_rate_table { 
enum qdisc_state_t {

	__QDISC_STATE_SCHED,

	__QDISC_STATE_DEACTIVATED,

	__QDISC_STATE_RUNNING,

};



struct qdisc_size_table {
@@ -102,6 +101,7 @@ struct Qdisc { 
	refcount_t		refcnt;



	spinlock_t		busylock ____cacheline_aligned_in_smp;

	spinlock_t		seqlock;

};



static inline void qdisc_refcount_inc(struct Qdisc *qdisc)
@@ -111,17 +111,17 @@ static inline void qdisc_refcount_inc(struct Qdisc *qdisc) 
	refcount_inc(&qdisc->refcnt);

}



static inline bool qdisc_is_running(const struct Qdisc *qdisc)

static inline bool qdisc_is_running(struct Qdisc *qdisc)

{

	if (qdisc->flags & TCQ_F_NOLOCK)

		return test_bit(__QDISC_STATE_RUNNING, &qdisc->state);

		return spin_is_locked(&qdisc->seqlock);

	return (raw_read_seqcount(&qdisc->running) & 1) ? true : false;

}



static inline bool qdisc_run_begin(struct Qdisc *qdisc)

{

	if (qdisc->flags & TCQ_F_NOLOCK) {

		if (test_and_set_bit(__QDISC_STATE_RUNNING, &qdisc->state))

		if (!spin_trylock(&qdisc->seqlock))

			return false;

	} else if (qdisc_is_running(qdisc)) {

		return false;
@@ -138,7 +138,7 @@ static inline void qdisc_run_end(struct Qdisc *qdisc) 
{

	write_seqcount_end(&qdisc->running);

	if (qdisc->flags & TCQ_F_NOLOCK)

		clear_bit(__QDISC_STATE_RUNNING, &qdisc->state);

		spin_unlock(&qdisc->seqlock);

}



static inline bool qdisc_may_bulk(const struct Qdisc *qdisc)

net/sched/sch_generic.c

+13 −2
Original line number Diff line number Diff line
@@ -656,7 +656,7 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc) 
		if (__skb_array_empty(q))

			continue;



		skb = skb_array_consume_bh(q);

		skb = __skb_array_consume(q);

	}

	if (likely(skb)) {

		qdisc_qstats_cpu_backlog_dec(qdisc, skb);
@@ -697,7 +697,7 @@ static void pfifo_fast_reset(struct Qdisc *qdisc) 
		if (!q->ring.queue)

			continue;



		while ((skb = skb_array_consume_bh(q)) != NULL)

		while ((skb = __skb_array_consume(q)) != NULL)

			kfree_skb(skb);

	}
@@ -858,6 +858,11 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, 
	lockdep_set_class(&sch->busylock,

			  dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);



	/* seqlock has the same scope of busylock, for NOLOCK qdisc */

	spin_lock_init(&sch->seqlock);

	lockdep_set_class(&sch->busylock,

			  dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);



	seqcount_init(&sch->running);

	lockdep_set_class(&sch->running,

			  dev->qdisc_running_key ?: &qdisc_running_key);
@@ -1097,6 +1102,10 @@ static void dev_deactivate_queue(struct net_device *dev, 


	qdisc = rtnl_dereference(dev_queue->qdisc);

	if (qdisc) {

		bool nolock = qdisc->flags & TCQ_F_NOLOCK;



		if (nolock)

			spin_lock_bh(&qdisc->seqlock);

		spin_lock_bh(qdisc_lock(qdisc));



		if (!(qdisc->flags & TCQ_F_BUILTIN))
@@ -1106,6 +1115,8 @@ static void dev_deactivate_queue(struct net_device *dev, 
		qdisc_reset(qdisc);



		spin_unlock_bh(qdisc_lock(qdisc));

		if (nolock)

			spin_unlock_bh(&qdisc->seqlock);

	}

}