[net-next,0/3] Some optimization for lockless qdisc

Message

Yunsheng Lin May 28, 2021, 2:49 a.m. UTC

Patch 1: remove unnecessary seqcount operation.
Patch 2: implement TCQ_F_CAN_BYPASS.
Patch 3: remove qdisc->empty.

Performance data for pktgen in queue_xmit mode + dummy netdev
with pfifo_fast:

 threads    unpatched           patched             delta
    1       2.60Mpps            3.21Mpps             +23%
    2       3.84Mpps            5.56Mpps             +44%
    4       5.52Mpps            5.58Mpps             +1%
    8       2.77Mpps            2.76Mpps             -0.3%
   16       2.24Mpps            2.23Mpps             +0.4%

Performance for IP forward testing: 1.05Mpps increases to
1.16Mpps, about 10% improvement.

V1: Drop RFC tag, Add nolock_qdisc_is_empty() and do the qdisc
    empty checking without the protection of qdisc->seqlock to
    aviod doing unnecessary spin_trylock() for contention case.
RFC v4: Use STATE_MISSED and STATE_DRAINING to indicate non-empty
        qdisc, and add patch 1 and 3.

Yunsheng Lin (3):
  net: sched: avoid unnecessary seqcount operation for lockless qdisc
  net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc
  net: sched: remove qdisc->empty for lockless qdisc

 include/net/sch_generic.h | 31 ++++++++++++++++++-------------
 net/core/dev.c            | 26 ++++++++++++++++++++++++--
 net/sched/sch_generic.c   | 23 ++++++++++++++++-------
 3 files changed, 58 insertions(+), 22 deletions(-)