netdev - Re: Packet gets stuck in NOLOCK pfifo

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Message-ID: <dd73f551d1fc89e457ffabd106cbf0bf401b747b.camel@redhat.com>
Date:   Thu, 03 Sep 2020 10:39:54 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Kehuan Feng <kehuan.feng@...il.com>
Cc:     Hillf Danton <hdanton@...a.com>, Jike Song <albcamus@...il.com>,
        Josh Hunt <johunt@...mai.com>,
        Jonas Bonn <jonas.bonn@...rounds.com>,
        Michael Zhivich <mzhivich@...mai.com>,
        David Miller <davem@...emloft.net>,
        John Fastabend <john.fastabend@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: Packet gets stuck in NOLOCK pfifo_fast qdisc

On Wed, 2020-09-02 at 22:01 -0700, Cong Wang wrote:
> Can you test the attached one-line fix? I think we are overthinking,
> probably all
> we need here is a busy wait.

I think that will solve, but I also think that will kill NOLOCK
performances due to really increased contention.

At this point I fear we could consider reverting the NOLOCK stuff.
I personally would hate doing so, but it looks like NOLOCK benefits are
outweighed by its issues.

Any other opinion more than welcome!

Cheers,

Paolo