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