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 and maintains an additional flag inside the qdisc struct, tracking the queue status (empty/not empty) and the second patch uses such info to implement the BYPASS code path for lockless qdisc. Overall this avoids up to 2 indirect calls per xmit packet when the packet rate is below line rate. Detailed performance figures are reported in the 2nd patch. 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 | 17 +++++++++++++++++ net/core/dev.c | 9 +++++++++ net/sched/sch_generic.c | 2 ++ 3 files changed, 28 insertions(+) -- 2.20.1
