Merge branch 'net-sched-singly-linked-list'
authorDavid S. Miller <davem@davemloft.net>
Mon, 19 Sep 2016 05:47:23 +0000 (01:47 -0400)
committerDavid S. Miller <davem@davemloft.net>
Mon, 19 Sep 2016 05:47:23 +0000 (01:47 -0400)
commit029ac211464f9cf87fa7aa51a6f01e41642d76c3
tree123595224534ee49f1175b6ef8371728b6d31538
parent106323b905a6bcd21ff83dd4e19566282fd5eb52
parent48da34b7a74201f15315cb1fc40bb9a7bd2b4940
Merge branch 'net-sched-singly-linked-list'

Florian Westphal says:

====================
sched: convert queues to single-linked list

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.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>