Re: [PATCH net-next 0/5] sched: convert queues to single-linked list

[David Miller]

From: Florian Westphal 
Date: Sun, 18 Sep 2016 00:57:29 +0200

> During Netfilter Workshop 2016 Eric Dumazet pointed out that qdisc
> schedulers use doubly-linked lists, even though single-linked list
> would be enough.
> 
> The double-linked skb lists incur one extra write on enqueue/dequeue
> operations (to change ->prev pointer of next list elem).
> 
> This series converts qdiscs to single-linked version, listhead
> maintains pointers to first (for dequeue) and last skb (for enqueue).
> 
> Most qdiscs don't queue at all and instead use a leaf qdisc (typically
> pfifo_fast) so only a few schedulers needed changes.
> 
> I briefly tested netem and htb and they seemed fine.
> 
> UDP_STREAM netperf with 64 byte packets via veth+pfifo_fast shows
> a small (~2%) improvement.

Series applied, thanks Florian.

[PATCH net-next 0/5] sched: convert queues to single-linked list

[Florian Westphal]

During Netfilter Workshop 2016 Eric Dumazet pointed out that qdisc
schedulers use doubly-linked lists, even though single-linked list
would be enough.

The double-linked skb lists incur one extra write on enqueue/dequeue
operations (to change ->prev pointer of next list elem).

This series converts qdiscs to single-linked version, listhead
maintains pointers to first (for dequeue) and last skb (for enqueue).

Most qdiscs don't queue at all and instead use a leaf qdisc (typically
pfifo_fast) so only a few schedulers needed changes.

I briefly tested netem and htb and they seemed fine.

UDP_STREAM netperf with 64 byte packets via veth+pfifo_fast shows
a small (~2%) improvement.

Florian Westphal (5):
  pie: use qdisc_dequeue_head wrapper
  sched: don't use skb queue helpers
  sched: remove qdisc arg from __qdisc_dequeue_head
  sched: replace __skb_dequeue with __qdisc_dequeue_head
  sched: add and use qdisc_skb_head helpers

 include/net/sch_generic.h |   72 +++---
 net/sched/sch_codel.c |4 +-
 net/sched/sch_fifo.c  |4 +-
 net/sched/sch_generic.c   |   30 +++
 net/sched/sch_htb.c   |   24 ---
 net/sched/sch_netem.c |   20 +---
 net/sched/sch_pie.c   |4 +-
 7 files changed, 115 insertions(+), 43 deletions(-)