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

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Date:   Sat, 23 Mar 2019 21:54:03 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com,
        john.fastabend@...il.com, ivecera@...hat.com
Subject: Re: [PATCH net-next v3 0/2] net: dev: BYPASS for lockless qdisc

From: Paolo Abeni <pabeni@...hat.com>
Date: Fri, 22 Mar 2019 16:01:54 +0100

> 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

Looks great, series applied, thanks Paolo.