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Date: Sat, 04 Oct 2014 10:11:31 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] net: sched: avoid costly atomic operation in
fq_dequeue()
From: Eric Dumazet <edumazet@...gle.com>
Standard qdisc API to setup a timer implies an atomic operation on every
packet dequeue : qdisc_unthrottled()
It turns out this is not really needed for FQ, as FQ has no concept of
global qdisc throttling, being a qdisc handling many different flows,
some of them can be throttled, while others are not.
Fix is straightforward : add a 'bool throttle' to
qdisc_watchdog_schedule_ns(), and remove calls to qdisc_unthrottled()
in sch_fq.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/pkt_sched.h | 4 ++--
net/sched/sch_api.c | 5 +++--
net/sched/sch_fq.c | 6 ++----
net/sched/sch_tbf.c | 3 ++-
4 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index e4b3c828c1c2..27a33833ff4a 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -65,12 +65,12 @@ struct qdisc_watchdog {
};
void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);
-void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires);
+void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires, bool throttle);
static inline void qdisc_watchdog_schedule(struct qdisc_watchdog *wd,
psched_time_t expires)
{
- qdisc_watchdog_schedule_ns(wd, PSCHED_TICKS2NS(expires));
+ qdisc_watchdog_schedule_ns(wd, PSCHED_TICKS2NS(expires), true);
}
void qdisc_watchdog_cancel(struct qdisc_watchdog *wd);
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index aa8329508dba..ab70e7dddb04 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -592,13 +592,14 @@ void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc)
}
EXPORT_SYMBOL(qdisc_watchdog_init);
-void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires)
+void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires, bool throttle)
{
if (test_bit(__QDISC_STATE_DEACTIVATED,
&qdisc_root_sleeping(wd->qdisc)->state))
return;
- qdisc_throttled(wd->qdisc);
+ if (throttle)
+ qdisc_throttled(wd->qdisc);
hrtimer_start(&wd->timer,
ns_to_ktime(expires),
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index c9b9fcb53206..cbd7e1fd23b4 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -377,7 +377,6 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
if (time_after(jiffies, f->age + q->flow_refill_delay))
f->credit = max_t(u32, f->credit, q->quantum);
q->inactive_flows--;
- qdisc_unthrottled(sch);
}
/* Note: this overwrites f->age */
@@ -385,7 +384,6 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
if (unlikely(f == &q->internal)) {
q->stat_internal_packets++;
- qdisc_unthrottled(sch);
}
sch->q.qlen++;
@@ -433,7 +431,8 @@ begin:
if (!head->first) {
if (q->time_next_delayed_flow != ~0ULL)
qdisc_watchdog_schedule_ns(&q->watchdog,
- q->time_next_delayed_flow);
+ q->time_next_delayed_flow,
+ false);
return NULL;
}
}
@@ -495,7 +494,6 @@ begin:
}
out:
qdisc_bstats_update(sch, skb);
- qdisc_unthrottled(sch);
return skb;
}
diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 77edffe329c4..a4afde14e865 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -268,7 +268,8 @@ static struct sk_buff *tbf_dequeue(struct Qdisc *sch)
}
qdisc_watchdog_schedule_ns(&q->watchdog,
- now + max_t(long, -toks, -ptoks));
+ now + max_t(long, -toks, -ptoks),
+ true);
/* Maybe we have a shorter packet in the queue,
which can be sent now. It sounds cool,
--
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