netdev - Re: [PATCH net-next v2 0/2] net: dev: BYPASS for lockless qdisc

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Date:   Fri, 22 Mar 2019 11:40:41 +0100
From:   Ivan Vecera <ivecera@...hat.com>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH net-next v2 0/2] net: dev: BYPASS for lockless qdisc

On 22. 03. 19 9:30, Paolo Abeni wrote:
> 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.
> 
>   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(+)
> 

Reviewed-by: Ivan Vecera <ivecera@...hat.com>