netdev - Re: [net v3 2/3] net: sched: add check tc_skip

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Date:   Tue, 30 Nov 2021 09:24:34 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        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>,
        Antoine Tenart <atenart@...nel.org>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Wei Wang <weiwan@...gle.com>,
        Björn Töpel <bjorn@...nel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [net v3 2/3] net: sched: add check tc_skip_classify in sch egress

On Tue, Nov 30, 2021 at 1:44 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Sun, Nov 28, 2021 at 8:55 PM <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 1 100); 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: 10662.33 tps, 108.95 Mbit/s
> >   After:  12434.48 tps, 145.89 Mbit/s
> >   For TCP_RR, there are 16.6% improvement, TCP_STREAM 33.9%.
>
> These numbers mean nothing, really.
>
> I think you should put 10,000 filters instead of 100 so that the
> numbers look even better ?
This 100 filters with different prio, I will install 10,000 filters
and test again. Thanks.
> As a matter of fact, you add yet another check in fast  path.
>
> For some reason I have not received the cover letter and patch 1/3.
1/3 patch, https://patchwork.kernel.org/project/netdevbpf/patch/20211129045503.20217-1-xiangxia.m.yue@gmail.com/


-- 
Best regards, Tonghao