From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
Yunsheng Lin <linyunsheng@huawei.com>,
David Miller <davem@davemloft.net>,
Vladimir Oltean <olteanv@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andriin@fb.com>,
Eric Dumazet <edumazet@google.com>, Wei Wang <weiwan@google.com>,
"Cong Wang ." <cong.wang@bytedance.com>,
Taehee Yoo <ap420073@gmail.com>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linuxarm@openeuler.org, Marc Kleine-Budde <mkl@pengutronix.de>,
linux-can@vger.kernel.org
Subject: Re: [RFC v2] net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc
Date: Wed, 17 Mar 2021 07:45:45 -0600 [thread overview]
Message-ID: <CAHmME9qDU7VRmBV+v0tzLiUpMJykjswSDwqc9P43ZwG1UD7mzw@mail.gmail.com> (raw)
In-Reply-To: <87eegddhsj.fsf@toke.dk>
On 3/17/21, Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> Cong Wang <xiyou.wangcong@gmail.com> writes:
>
>> On Mon, Mar 15, 2021 at 2:07 PM Jakub Kicinski <kuba@kernel.org> wrote:
>>>
>>> I thought pfifo was supposed to be "lockless" and this change
>>> re-introduces a lock between producer and consumer, no?
>>
>> It has never been truly lockless, it uses two spinlocks in the ring
>> buffer
>> implementation, and it introduced a q->seqlock recently, with this patch
>> now we have priv->lock, 4 locks in total. So our "lockless" qdisc ends
>> up having more locks than others. ;) I don't think we are going to a
>> right direction...
>
> Just a thought, have you guys considered adopting the lockless MSPC ring
> buffer recently introduced into Wireguard in commit:
>
> 8b5553ace83c ("wireguard: queueing: get rid of per-peer ring buffers")
>
> Jason indicated he was willing to work on generalising it into a
> reusable library if there was a use case for it. I haven't quite though
> through the details of whether this would be such a use case, but
> figured I'd at least mention it :)
That offer definitely still stands. Generalization sounds like a lot of fun.
Keep in mind though that it's an eventually consistent queue, not an
immediately consistent one, so that might not match all use cases. It
works with wg because we always trigger the reader thread anew when it
finishes, but that doesn't apply to everyone's queueing setup.
next prev parent reply other threads:[~2021-03-17 13:46 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-13 2:47 [PATCH RFC] net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc Yunsheng Lin
2021-03-14 0:03 ` Vladimir Oltean
2021-03-14 10:15 ` Marc Kleine-Budde
2021-03-15 0:50 ` Yunsheng Lin
2021-03-15 3:10 ` [RFC v2] " Yunsheng Lin
2021-03-15 12:29 ` Vladimir Oltean
2021-03-15 13:09 ` Marc Kleine-Budde
2021-03-15 18:53 ` Jakub Kicinski
2021-03-16 0:35 ` Yunsheng Lin
2021-03-16 3:47 ` [Linuxarm] " Yunsheng Lin
2021-03-16 8:15 ` Eric Dumazet
2021-03-16 12:36 ` Yunsheng Lin
2021-03-16 22:48 ` Cong Wang
2021-03-17 1:14 ` Yunsheng Lin
2021-03-17 13:35 ` Toke Høiland-Jørgensen
2021-03-17 13:45 ` Jason A. Donenfeld [this message]
2021-03-18 7:33 ` [Linuxarm] " Yunsheng Lin
2021-03-19 18:15 ` Cong Wang
2021-03-22 0:55 ` Yunsheng Lin
2021-03-24 1:49 ` Cong Wang
2021-03-24 2:36 ` Yunsheng Lin
2021-03-19 19:03 ` Jason A. Donenfeld
2021-03-22 1:05 ` Yunsheng Lin
2021-03-18 7:10 ` Ahmad Fatoum
2021-03-18 7:46 ` Yunsheng Lin
2021-03-18 9:09 ` Ahmad Fatoum
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