From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Yunsheng Lin <linyunsheng@huawei.com>,
davem@davemloft.net, kuba@kernel.org, olteanv@gmail.com
Cc: ast@kernel.org, daniel@iogearbox.net, andriin@fb.com,
edumazet@google.com, weiwan@google.com, cong.wang@bytedance.com,
ap420073@gmail.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, linuxarm@openeuler.org,
linux-can@vger.kernel.org
Subject: Re: [RFC v2] net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc
Date: Mon, 15 Mar 2021 14:09:33 +0100 [thread overview]
Message-ID: <4b02d9bb-772f-ff40-b865-ea87bd1bea6e@pengutronix.de> (raw)
In-Reply-To: <1615777818-13969-1-git-send-email-linyunsheng@huawei.com>
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On 3/15/21 4:10 AM, Yunsheng Lin wrote:
> Currently pfifo_fast has both TCQ_F_CAN_BYPASS and TCQ_F_NOLOCK
> flag set, but queue discipline by-pass does not work for lockless
> qdisc because skb is always enqueued to qdisc even when the qdisc
> is empty, see __dev_xmit_skb().
>
> This patch calls sch_direct_xmit() to transmit the skb directly
> to the driver for empty lockless qdisc too, which aviod enqueuing
> and dequeuing operation. qdisc->empty is set to false whenever a
> skb is enqueued, see pfifo_fast_enqueue(), and is set to true when
> skb dequeuing return NULL, see pfifo_fast_dequeue(), a spinlock is
> added to avoid the race between enqueue/dequeue and qdisc->empty
> setting.
>
> If there is requeued skb in q->gso_skb, and qdisc->empty is true,
> do not allow bypassing requeued skb. enqueuing and dequeuing in
> q->gso_skb is always protected by qdisc->seqlock, so is the access
> of q->gso_skb by skb_queue_empty();
>
> Also, qdisc is scheduled at the end of qdisc_run_end() when q->empty
> is false to avoid packet stuck problem.
>
> The performance for ip_forward test increases about 10% with this
> patch.
>
> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
I gave it a short test on a single core imx. No problem here.
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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next prev parent reply other threads:[~2021-03-15 13:10 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1615603667-22568-1-git-send-email-linyunsheng@huawei.com>
[not found] ` <20210314000350.2mrhvprsi77qwqdi@skbuf>
2021-03-14 10:15 ` [PATCH RFC] net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc 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 [this message]
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
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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