linux-kernel - Re: [Linuxarm] [PATCH net] net: sched: fix packet stuck problem for lockless qdisc

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Message-ID: <CAM_iQpV4HX5L1b8ofUig-bi3r_MDdsjThqaxfoRCd=02XZBprQ@mail.gmail.com>
Date:   Fri, 19 Mar 2021 12:45:30 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Vladimir Oltean <olteanv@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Eric Dumazet <edumazet@...gle.com>,
        Wei Wang <weiwan@...gle.com>,
        "Cong Wang ." <cong.wang@...edance.com>,
        Taehee Yoo <ap420073@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linuxarm@...neuler.org,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-can@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>, kpsingh@...nel.org,
        bpf <bpf@...r.kernel.org>, Jonas Bonn <jonas.bonn@...rounds.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Michael Zhivich <mzhivich@...mai.com>,
        Josh Hunt <johunt@...mai.com>, Jike Song <albcamus@...il.com>,
        Kehuan Feng <kehuan.feng@...il.com>,
        Ahmad Fatoum <a.fatoum@...gutronix.de>
Subject: Re: [Linuxarm] [PATCH net] net: sched: fix packet stuck problem for
 lockless qdisc

On Fri, Mar 19, 2021 at 2:25 AM Yunsheng Lin <linyunsheng@...wei.com> wrote:
> I had done some performance test to see if there is value to
> fix the packet stuck problem and support lockless qdisc bypass,
> here is some result using pktgen in 'queue_xmit' mode on a dummy
> device as Paolo Abeni had done in [1], and using pfifo_fast qdisc:
>
> threads  vanilla    locked-qdisc    vanilla+this_patch
>    1     2.6Mpps      2.9Mpps            2.5Mpps
>    2     3.9Mpps      4.8Mpps            3.6Mpps
>    4     5.6Mpps      3.0Mpps            4.7Mpps
>    8     2.7Mpps      1.6Mpps            2.8Mpps
>    16    2.2Mpps      1.3Mpps            2.3Mpps
>
> locked-qdisc: test by removing the "TCQ_F_NOLOCK | TCQ_F_CPUSTATS".

I read this as this patch introduces somehow a performance
regression for -net, as the lockless bypass patch you submitted is
for -net-next.

Thanks.