netdev - [PATCH net-next v3 0/2] net: dev: BYPASS for lockless qdisc

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Date:   Fri, 22 Mar 2019 16:01:54 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        John Fastabend <john.fastabend@...il.com>,
        Ivan Vecera <ivecera@...hat.com>
Subject: [PATCH net-next v3 0/2] net: dev: BYPASS for lockless qdisc

This patch series is aimed at improving xmit performances of lockless qdisc
in the uncontended scenario.

After the lockless refactor pfifo_fast can't leverage the BYPASS optimization.
Due to retpolines the overhead for the avoidables enqueue and dequeue operations
has increased and we see measurable regressions.

The first patch introduces the BYPASS code path for lockless qdisc, and the
second one optimizes such path further. Overall this avoids up to 3 indirect
calls per xmit packet. Detailed performance figures are reported in the 2nd
patch.

 v2 -> v3:
  - qdisc_is_empty() has a const argument (Eric)

 v1 -> v2:
  - use really an 'empty' flag instead of 'not_empty', as
    suggested by Eric

Paolo Abeni (2):
  net: sched: add empty status flag for NOLOCK qdisc
  net: dev: introduce support for sch BYPASS for lockless qdisc

 include/net/sch_generic.h | 11 +++++++++++
 net/core/dev.c            |  9 +++++++++
 net/sched/sch_generic.c   |  3 +++
 3 files changed, 23 insertions(+)

-- 
2.20.1