linux-toradex.git/net/sched/sch_htb.c, branch v4.9.119

sched: add and use qdisc_skb_head helpers

2016-09-19T05:47:18+00:00

This change replaces sk_buff_head struct in Qdiscs with new qdisc_skb_head.

Its similar to the skb_buff_head api, but does not use skb->prev pointers.

Qdiscs will commonly enqueue at the tail of a list and dequeue at head.
While skb_buff_head works fine for this, enqueue/dequeue needs to also
adjust the prev pointer of next element.

The ->prev pointer is not required for qdiscs so we can just leave
it undefined and avoid one cacheline write access for en/dequeue.

Suggested-by: Eric Dumazet 
Signed-off-by: Florian Westphal 
Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2016-07-24T04:53:32+00:00

Just several instances of overlapping changes.

Signed-off-by: David S. Miller

net/sched/sch_htb: clamp xstats tokens to fit into 32-bit int

2016-07-19T05:44:31+00:00

In kernel HTB keeps tokens in signed 64-bit in nanoseconds. In netlink
protocol these values are converted into pshed ticks (64ns for now) and
truncated to 32-bit. In struct tc_htb_xstats fields "tokens" and "ctokens"
are declared as unsigned 32-bit but they could be negative thus tool 'tc'
prints them as signed. Big values loose higher bits and/or become negative.

This patch clamps tokens in xstat into range from INT_MIN to INT_MAX.
In this way it's easier to understand what's going on here.

Signed-off-by: Konstantin Khlebnikov 
Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2016-06-30T09:03:36+00:00

Several cases of overlapping changes, except the packet scheduler
conflicts which deal with the addition of the free list parameter
to qdisc_enqueue().

Signed-off-by: David S. Miller

net_sched: sch_htb: export class backlog in dumps

2016-06-25T16:19:35+00:00

We already get child qdisc qlen, we also can get its backlog
so that class dumps can report it.

Also replace qstats by a single drop counter, but move it in
a separate cache line so that drops do not dirty useful cache lines.

Tested:

$ tc -s cl sh dev eth0
class htb 1:1 root leaf 3: prio 0 rate 1Gbit ceil 1Gbit burst 500000b cburst 500000b
 Sent 2183346912 bytes 9021815 pkt (dropped 2340774, overlimits 0 requeues 0)
 rate 1001Mbit 517543pps backlog 120758b 499p requeues 0
 lended: 9021770 borrowed: 0 giants: 0
 tokens: 9 ctokens: 9

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

net_sched: drop packets after root qdisc lock is released

2016-06-25T16:19:35+00:00

Qdisc performance suffers when packets are dropped at enqueue()
time because drops (kfree_skb()) are done while qdisc lock is held,
delaying a dequeue() draining the queue.

Nominal throughput can be reduced by 50 % when this happens,
at a time we would like the dequeue() to proceed as fast as possible.

Even FQ is vulnerable to this problem, while one of FQ goals was
to provide some flow isolation.

This patch adds a 'struct sk_buff **to_free' parameter to all
qdisc->enqueue(), and in qdisc_drop() helper.

I measured a performance increase of up to 12 %, but this patch
is a prereq so that future batches in enqueue() can fly.

Signed-off-by: Eric Dumazet 
Acked-by: Jesper Dangaard Brouer 
Signed-off-by: David S. Miller

htb: call qdisc_root with rcu read lock held

2016-06-15T21:42:46+00:00

saw a debug splat:
net/include/net/sch_generic.h:287 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
 2 locks held by kworker/2:1/710:
  #0:  ("events"){.+.+.+}, at: []
  #1:  ((&q->work)){+.+...}, at: [] process_one_work+0x14d/0x690
Workqueue: events htb_work_func
Call Trace:
 [] dump_stack+0x85/0xc2
 [] lockdep_rcu_suspicious+0xe7/0x120
 [] htb_work_func+0x67/0x70

Signed-off-by: Florian Westphal 
Acked-by: Cong Wang 
Signed-off-by: David S. Miller

net_sched: sch_htb: defer skb freeing

2016-06-15T21:08:35+00:00

Both htb_reset() and htb_destroy() can use __qdisc_reset_queue()
instead of __skb_queue_purge() to defer skb freeing of internal
queues.

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

net_sched: remove generic throttled management

2016-06-11T06:58:21+00:00

__QDISC_STATE_THROTTLED bit manipulation is rather expensive
for HTB and few others.

I already removed it for sch_fq in commit f2600cf02b5b
("net: sched: avoid costly atomic operation in fq_dequeue()")
and so far nobody complained.

When one ore more packets are stuck in one or more throttled
HTB class, a htb dequeue() performs two atomic operations
to clear/set __QDISC_STATE_THROTTLED bit, while root qdisc
lock is held.

Removing this pair of atomic operations bring me a 8 % performance
increase on 200 TCP_RR tests, in presence of throttled classes.

This patch has no side effect, since nothing actually uses
disc_is_throttled() anymore.

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

sched: remove qdisc->drop

2016-06-09T06:58:52+00:00

after removal of TCA_CBQ_OVL_STRATEGY from cbq scheduler, there are no
more callers of ->drop() outside of other ->drop functions, i.e.
nothing calls them.

Signed-off-by: Florian Westphal 
Signed-off-by: David S. Miller