netdev - Re: [net v4 2/3] net: sched: add check tc_skip

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Message-ID: <CAMDZJNUGyipTQgDv+M8_kiOEZwXJnivZo6KCwgYy_BoMOiEZew@mail.gmail.com>
Date:   Sat, 4 Dec 2021 09:42:48 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        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>,
        Antoine Tenart <atenart@...nel.org>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Wei Wang <weiwan@...gle.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [net v4 2/3] net: sched: add check tc_skip_classify in sch egress

On Sat, Dec 4, 2021 at 5:35 AM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On 12/2/21 3:47 AM, xiangxia.m.yue@...il.com wrote:
> > From: Tonghao Zhang <xiangxia.m.yue@...il.com>
> >
> > Try to resolve the issues as below:
> > * We look up and then check tc_skip_classify flag in net
> >    sched layer, even though skb don't want to be classified.
> >    That case may consume a lot of cpu cycles.
> >
> >    Install the rules as below:
> >    $ for id in $(seq 1 10000); do
> >    $       tc filter add ... egress prio $id ... action mirred egress redirect dev ifb0
> >    $ done
> >
> >    netperf:
> >    $ taskset -c 1 netperf -t TCP_RR -H ip -- -r 32,32
> >    $ taskset -c 1 netperf -t TCP_STREAM -H ip -- -m 32
> >
> >    Before: 152.04 tps, 0.58 Mbit/s
> >    After:  303.07 tps, 1.51 Mbit/s
> >    For TCP_RR, there are 99.3% improvement, TCP_STREAM 160.3%.
>
> As it was pointed out earlier by Eric in v3, these numbers are moot since noone
> is realistically running such a setup in practice with 10k linear rules.
Yes. As I said in v1, in production, we use the 5+ prio. With this
patch, little improvements, 1.x%

This patch also fixes the packets loopback, if we use the bpf_redirect
to ifb in egress path.

-- 
Best regards, Tonghao