netdev - Re: [PATCH v2 net-next 0/6] skbuff: micro-optimize flow dissection

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Date:   Sat, 13 Mar 2021 13:30:24 +0000
From:   Alexander Lobakin <alobakin@...me>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Alexander Lobakin <alobakin@...me>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Kevin Hao <haokexin@...il.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Marco Elver <elver@...gle.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Ariel Levkovich <lariel@...lanox.com>,
        Wang Qing <wangqing@...o.com>,
        Davide Caratti <dcaratti@...hat.com>,
        Guillaume Nault <gnault@...hat.com>,
        Eran Ben Elisha <eranbe@...dia.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 net-next 0/6] skbuff: micro-optimize flow dissection

From: Alexander Lobakin <alobakin@...me>
Date: Sat, 13 Mar 2021 11:37:03 +0000

> This little number makes all of the flow dissection functions take
> raw input data pointer as const (1-5) and shuffles the branches in
> __skb_header_pointer() according to their hit probability.
>
> The result is +20 Mbps per flow/core with one Flow Dissector pass
> per packet. This affects RPS (with software hashing), drivers that
> use eth_get_headlen() on their Rx path and so on.
>
> Since v1 [0]:
>  - rebase on top of the latest net-next. This was super-weird, but
>    I double-checked that the series applies with no conflicts, and
>    then on Patchwork it didn't;

Still failing on Patchwork. I rebased it ten thousand times, rebuilt
the patches manually, tried previous stable Git version and the
latest CVS snapshot, and always got the same series that successfully
applies to next-next.
Can you please take a look?

>  - no other changes.
>
> [0] https://lore.kernel.org/netdev/20210312194538.337504-1-alobakin@pm.me
>
> Alexander Lobakin (6):
>   flow_dissector: constify bpf_flow_dissector's data pointers
>   skbuff: make __skb_header_pointer()'s data argument const
>   flow_dissector: constify raw input @data argument
>   linux/etherdevice.h: misc trailing whitespace cleanup
>   ethernet: constify eth_get_headlen()'s @data argument
>   skbuff: micro-optimize {,__}skb_header_pointer()
>
>  include/linux/etherdevice.h  |  4 ++--
>  include/linux/skbuff.h       | 26 +++++++++++------------
>  include/net/flow_dissector.h |  6 +++---
>  net/core/flow_dissector.c    | 41 +++++++++++++++++++-----------------
>  net/ethernet/eth.c           |  2 +-
>  5 files changed, 40 insertions(+), 39 deletions(-)
>
> --
> 2.30.2

Thanks,
Al