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author | Paolo Abeni <pabeni@redhat.com> | 2018-05-15 10:50:31 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2018-05-16 12:26:25 -0400 |
commit | 32f7b44d0f5661044fcfa84e9ad402ed9d759107 (patch) | |
tree | d2453e21a4187e32c9da74a25bbfee4446e725b5 /net/sched | |
parent | 5a63f77af7d69deb02a92b60d61141fe687997f8 (diff) | |
download | linux-32f7b44d0f5661044fcfa84e9ad402ed9d759107.tar.gz linux-32f7b44d0f5661044fcfa84e9ad402ed9d759107.tar.bz2 linux-32f7b44d0f5661044fcfa84e9ad402ed9d759107.zip |
sched: manipulate __QDISC_STATE_RUNNING in qdisc_run_* helpers
Currently NOLOCK qdiscs pay a measurable overhead to atomically
manipulate the __QDISC_STATE_RUNNING. Such bit is flipped twice per
packet in the uncontended scenario with packet rate below the
line rate: on packed dequeue and on the next, failing dequeue attempt.
This changeset moves the bit manipulation into the qdisc_run_{begin,end}
helpers, so that the bit is now flipped only once per packet, with
measurable performance improvement in the uncontended scenario.
This also allows simplifying the qdisc teardown code path - since
qdisc_is_running() is now effective for each qdisc type - and avoid a
possible race between qdisc_run() and dev_deactivate_many(), as now
the some_qdisc_is_busy() can properly detect NOLOCK qdiscs being busy
dequeuing packets.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
-rw-r--r-- | net/sched/sch_generic.c | 31 |
1 files changed, 9 insertions, 22 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 39c144b6ff98..ff3ce71aec93 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -373,33 +373,24 @@ bool sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q, */ static inline bool qdisc_restart(struct Qdisc *q, int *packets) { - bool more, validate, nolock = q->flags & TCQ_F_NOLOCK; spinlock_t *root_lock = NULL; struct netdev_queue *txq; struct net_device *dev; struct sk_buff *skb; + bool validate; /* Dequeue packet */ - if (nolock && test_and_set_bit(__QDISC_STATE_RUNNING, &q->state)) - return false; - skb = dequeue_skb(q, &validate, packets); - if (unlikely(!skb)) { - if (nolock) - clear_bit(__QDISC_STATE_RUNNING, &q->state); + if (unlikely(!skb)) return false; - } - if (!nolock) + if (!(q->flags & TCQ_F_NOLOCK)) root_lock = qdisc_lock(q); dev = qdisc_dev(q); txq = skb_get_tx_queue(dev, skb); - more = sch_direct_xmit(skb, q, dev, txq, root_lock, validate); - if (nolock) - clear_bit(__QDISC_STATE_RUNNING, &q->state); - return more; + return sch_direct_xmit(skb, q, dev, txq, root_lock, validate); } void __qdisc_run(struct Qdisc *q) @@ -1131,17 +1122,13 @@ static bool some_qdisc_is_busy(struct net_device *dev) dev_queue = netdev_get_tx_queue(dev, i); q = dev_queue->qdisc_sleeping; - if (q->flags & TCQ_F_NOLOCK) { - val = test_bit(__QDISC_STATE_SCHED, &q->state); - } else { - root_lock = qdisc_lock(q); - spin_lock_bh(root_lock); + root_lock = qdisc_lock(q); + spin_lock_bh(root_lock); - val = (qdisc_is_running(q) || - test_bit(__QDISC_STATE_SCHED, &q->state)); + val = (qdisc_is_running(q) || + test_bit(__QDISC_STATE_SCHED, &q->state)); - spin_unlock_bh(root_lock); - } + spin_unlock_bh(root_lock); if (val) return true; |