linux/include/net/sch_generic.h, branch v4.9

sched: add and use qdisc_skb_head helpers

2016-09-19T05:47:18Z

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

sched: remove qdisc arg from __qdisc_dequeue_head

2016-09-19T05:47:18Z

Moves qdisc stat accouting to qdisc_dequeue_head. The only direct caller of the __qdisc_dequeue_head version open-codes this now. This allows us to later use __qdisc_dequeue_head as a replacement of __skb_dequeue() (which operates on sk_buff_head list). Signed-off-by: Florian Westphal Signed-off-by: David S. Miller

net: minor optimization in qdisc_qstats_cpu_drop()

2016-08-25T23:45:29Z

per_cpu_inc() is faster (at least on x86) than per_cpu_ptr(xxx)++; Signed-off-by: Eric Dumazet Acked-by: John Fastabend Signed-off-by: David S. Miller

net: sched: convert qdisc linked list to hashtable

2016-08-11T00:19:02Z

Convert the per-device linked list into a hashtable. The primary motivation for this change is that currently, we're not tracking all the qdiscs in hierarchy (e.g. excluding default qdiscs), as the lookup performed over the linked list by qdisc_match_from_root() is rather expensive. The ultimate goal is to get rid of hidden qdiscs completely, which will bring much more determinism in user experience. Reviewed-by: Cong Wang Signed-off-by: Jiri Kosina Signed-off-by: David S. Miller

net_sched: generalize bulk dequeue

2016-06-25T16:19:35Z

When qdisc bulk dequeue was added in linux-3.18 (commit 5772e9a3463b "qdisc: bulk dequeue support for qdiscs with TCQ_F_ONETXQUEUE"), it was constrained to some specific qdiscs. With some extra care, we can extend this to all qdiscs, so that typical traffic shaping solutions can benefit from small batches (8 packets in this patch). For example, HTB is often used on some multi queue device. And bonding/team are multi queue devices... Idea is to bulk-dequeue packets mapping to the same transmit queue. This brings between 35 and 80 % performance increase in HTB setup under pressure on a bonding setup : 1) NUMA node contention : 610,000 pps -> 1,110,000 pps 2) No node contention : 1,380,000 pps -> 1,930,000 pps Now we should work to add batches on the enqueue() side ;) Signed-off-by: Eric Dumazet Cc: John Fastabend Cc: Jesper Dangaard Brouer Cc: Hannes Frederic Sowa Cc: Florian Westphal Cc: Daniel Borkmann Acked-by: Jesper Dangaard Brouer Signed-off-by: David S. Miller

net_sched: drop packets after root qdisc lock is released

2016-06-25T16:19:35Z

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

net_sched: add the ability to defer skb freeing

2016-06-15T21:08:34Z

qdisc are changed under RTNL protection and often while blocking BH and root qdisc spinlock. When lots of skbs need to be dropped, we free them under these locks causing TX/RX freezes, and more generally latency spikes. This commit adds rtnl_kfree_skbs(), used to queue skbs for deferred freeing. Actual freeing happens right after RTNL is released, with appropriate scheduling points. rtnl_qdisc_drop() can also be used in place of disc_drop() when RTNL is held. qdisc_reset_queue() and __qdisc_reset_queue() get the new behavior, so standard qdiscs like pfifo, pfifo_fast... have their ->reset() method automatically handled. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

net_sched: remove generic throttled management

2016-06-11T06:58:21Z

__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

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

2016-06-10T18:52:24Z

Conflicts: net/sched/act_police.c net/sched/sch_drr.c net/sched/sch_hfsc.c net/sched/sch_prio.c net/sched/sch_red.c net/sched/sch_tbf.c In net-next the drop methods of the packet schedulers got removed, so the bug fixes to them in 'net' are irrelevant. A packet action unload crash fix conflicts with the addition of the new firstuse timestamp. Signed-off-by: David S. Miller

net: sched: fix qdisc->running lockdep annotations

2016-06-09T20:28:37Z

1) qdisc_run_begin() is really using the equivalent of a trylock. Instead of using write_seqcount_begin(), use a combination of raw_write_seqcount_begin() and correct lockdep annotation. 2) sch_direct_xmit() should use regular spin_lock(root_lock) Fixes: f9eb8aea2a1e ("net_sched: transform qdisc running bit into a seqcount") Signed-off-by: Eric Dumazet Reported-by: David Ahern Signed-off-by: David S. Miller