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| author | Paolo Abeni <pabeni@redhat.com> | 2019-03-22 16:01:55 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2019-03-23 21:52:36 -0400 |
| commit | 28cff537ef2eed9307bc7e4e40745075637bec56 (patch) | |
| tree | 19e12fe1c09bd817cae2410b5dd0b68ff6c21e43 /net/sched/sch_generic.c | |
| parent | 576fd2f7cac3daa36025f0039f9e7cb75b4b4ae0 (diff) | |
| download | lwn-28cff537ef2eed9307bc7e4e40745075637bec56.tar.gz lwn-28cff537ef2eed9307bc7e4e40745075637bec56.zip | |
net: sched: add empty status flag for NOLOCK qdisc
The queue is marked not empty after acquiring the seqlock,
and it's up to the NOLOCK qdisc clearing such flag on dequeue.
Since the empty status lays on the same cache-line of the
seqlock, it's always hot on cache during the updates.
This makes the empty flag update a little bit loosy. Given
the lack of synchronization between enqueue and dequeue, this
is unavoidable.
v2 -> v3:
- qdisc_is_empty() has a const argument (Eric)
v1 -> v2:
- use really an 'empty' flag instead of 'not_empty', as
suggested by Eric
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_generic.c')
| -rw-r--r-- | net/sched/sch_generic.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index a117d9260558..81356ef38d1d 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -671,6 +671,8 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc) qdisc_qstats_cpu_backlog_dec(qdisc, skb); qdisc_bstats_cpu_update(qdisc, skb); qdisc_qstats_atomic_qlen_dec(qdisc); + } else { + qdisc->empty = true; } return skb; @@ -880,6 +882,7 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, sch->enqueue = ops->enqueue; sch->dequeue = ops->dequeue; sch->dev_queue = dev_queue; + sch->empty = true; dev_hold(dev); refcount_set(&sch->refcnt, 1); |