From: Kehuan Feng <kehuan.feng@gmail.com>
To: Hillf Danton <hdanton@sina.com>
Cc: Jike Song <albcamus@gmail.com>, Josh Hunt <johunt@akamai.com>,
Paolo Abeni <pabeni@redhat.com>,
Jonas Bonn <jonas.bonn@netrounds.com>,
Cong Wang <xiyou.wangcong@gmail.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>
Subject: Re: Packet gets stuck in NOLOCK pfifo_fast qdisc
Date: Wed, 26 Aug 2020 10:38:43 +0800 [thread overview]
Message-ID: <CACS=qqKgiwdCR_5+z-vkZ0X8DfzOPD7_ooJ_imeBnx+X1zw2qg@mail.gmail.com> (raw)
In-Reply-To: <20200825162329.11292-1-hdanton@sina.com>
Hi Hillf,
Thanks for the patch.
I just tried it and it looks better than previous one. The issue
appeared only once over ~30 mins stressing (without the patch , it
shows up within 1 mins in usual, so I feel like we are getting close
to the final fix)
(pasted the modifications on my tree in case of any missing)
--- ./include/net/sch_generic.h.orig 2020-08-21 15:13:51.787952710 +0800
+++ ./include/net/sch_generic.h 2020-08-26 09:41:04.647173869 +0800
@@ -79,6 +79,7 @@
#define TCQ_F_INVISIBLE 0x80 /* invisible by default in dump */
#define TCQ_F_NOLOCK 0x100 /* qdisc does not require locking */
#define TCQ_F_OFFLOADED 0x200 /* qdisc is offloaded to HW */
+ int pkt_seq;
u32 limit;
const struct Qdisc_ops *ops;
struct qdisc_size_table __rcu *stab;
--- ./include/net/pkt_sched.h.orig 2020-08-21 15:13:51.787952710 +0800
+++ ./include/net/pkt_sched.h 2020-08-26 09:42:14.491377514 +0800
@@ -117,8 +117,15 @@
static inline void qdisc_run(struct Qdisc *q)
{
if (qdisc_run_begin(q)) {
+ q->pkt_seq = 0;
+
__qdisc_run(q);
qdisc_run_end(q);
+
+ /* reschedule qdisc if there are packets enqueued */
+ if (q->pkt_seq != 0)
+ __netif_schedule(q);
+
}
}
--- ./net/core/dev.c.orig 2020-03-19 16:31:27.000000000 +0800
+++ ./net/core/dev.c 2020-08-26 09:47:57.783165885 +0800
@@ -2721,6 +2721,7 @@
local_irq_save(flags);
sd = this_cpu_ptr(&softnet_data);
+ q->pkt_seq = 0;
q->next_sched = NULL;
*sd->output_queue_tailp = q;
sd->output_queue_tailp = &q->next_sched;
--- ./net/sched/sch_generic.c.orig 2020-08-24 22:02:04.589830751 +0800
+++ ./net/sched/sch_generic.c 2020-08-26 09:43:40.987852551 +0800
@@ -403,6 +403,9 @@
*/
quota -= packets;
if (quota <= 0 || need_resched()) {
+ /* info caller to reschedule qdisc outside q->seqlock */
+ q->pkt_seq = 1;
+
__netif_schedule(q);
break;
}
Hillf Danton <hdanton@sina.com> 于2020年8月26日周三 上午12:26写道:
>
>
> Hi Feng,
>
> On Tue, 25 Aug 2020 15:14:12 +0800 Fengkehuan Feng wrote:
> > Hi Hillf,
> >
> > I just tried the updated version and the system can boot up now.
>
> Thanks again for your testing.
>
> > It does mitigate the issue a lot but still couldn't get rid of it
> > thoroughly. It seems to me like the effect of Cong's patch.
>
> Your echoes show we're still march in the dark and let's try another
> direction in which qdisc is rescheduled outside seqlock to make sure
> tx softirq is raised when there're more packets on the pfifo_fast to
> be transmitted.
>
> CPU0 CPU1
> ---- ----
> seqlock
> test __QDISC_STATE_SCHED
> raise tx softirq
> clear __QDISC_STATE_SCHED
> try seqlock
> __qdisc_run(q);
> sequnlock
> sequnlock
>
>
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -79,6 +79,7 @@ struct Qdisc {
> #define TCQ_F_INVISIBLE 0x80 /* invisible by default in dump */
> #define TCQ_F_NOLOCK 0x100 /* qdisc does not require locking */
> #define TCQ_F_OFFLOADED 0x200 /* qdisc is offloaded to HW */
> + int pkt_seq;
> u32 limit;
> const struct Qdisc_ops *ops;
> struct qdisc_size_table __rcu *stab;
> --- a/include/net/pkt_sched.h
> +++ b/include/net/pkt_sched.h
> @@ -118,6 +118,8 @@ void __qdisc_run(struct Qdisc *q);
> static inline void qdisc_run(struct Qdisc *q)
> {
> if (qdisc_run_begin(q)) {
> + q->pkt_seq = 0;
> +
> /* NOLOCK qdisc must check 'state' under the qdisc seqlock
> * to avoid racing with dev_qdisc_reset()
> */
> @@ -125,6 +127,10 @@ static inline void qdisc_run(struct Qdis
> likely(!test_bit(__QDISC_STATE_DEACTIVATED, &q->state)))
> __qdisc_run(q);
> qdisc_run_end(q);
> +
> + /* reschedule qdisc if there are packets enqueued */
> + if (q->pkt_seq != 0)
> + __netif_schedule(q);
> }
> }
>
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -384,6 +384,8 @@ void __qdisc_run(struct Qdisc *q)
> while (qdisc_restart(q, &packets)) {
> quota -= packets;
> if (quota <= 0) {
> + /* info caller to reschedule qdisc outside q->seqlock */
> + q->pkt_seq = 1;
> __netif_schedule(q);
> break;
> }
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3031,6 +3031,7 @@ static void __netif_reschedule(struct Qd
>
> local_irq_save(flags);
> sd = this_cpu_ptr(&softnet_data);
> + q->pkt_seq = 0;
> q->next_sched = NULL;
> *sd->output_queue_tailp = q;
> sd->output_queue_tailp = &q->next_sched;
> --
>
next prev parent reply other threads:[~2020-08-26 2:38 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 6:46 Packet gets stuck in NOLOCK pfifo_fast qdisc Jonas Bonn
2019-10-09 19:14 ` Paolo Abeni
2019-10-10 6:27 ` Jonas Bonn
2019-10-11 0:39 ` Jonas Bonn
2020-06-23 13:42 ` Michael Zhivich
2020-06-30 19:14 ` Josh Hunt
2020-07-01 7:53 ` Jonas Bonn
2020-07-01 16:05 ` Cong Wang
2020-07-01 19:58 ` Cong Wang
2020-07-01 22:02 ` Josh Hunt
2020-07-02 6:14 ` Jonas Bonn
2020-07-02 9:45 ` Paolo Abeni
2020-07-02 18:08 ` Josh Hunt
2020-07-07 14:18 ` Paolo Abeni
2020-07-08 20:16 ` Cong Wang
2020-07-09 9:20 ` Paolo Abeni
2020-07-08 20:33 ` Zhivich, Michael
2020-08-20 7:43 ` Jike Song
2020-08-20 18:13 ` Josh Hunt
[not found] ` <20200822032800.16296-1-hdanton@sina.com>
2020-08-25 2:18 ` Fengkehuan Feng
[not found] ` <20200825032312.11776-1-hdanton@sina.com>
2020-08-25 7:14 ` Fengkehuan Feng
[not found] ` <20200825162329.11292-1-hdanton@sina.com>
2020-08-26 2:38 ` Kehuan Feng [this message]
[not found] ` <CACS=qqKptAQQGiMoCs1Zgs9S4ZppHhasy1AK4df2NxnCDR+vCw@mail.gmail.com>
[not found] ` <5f46032e.1c69fb81.9880c.7a6cSMTPIN_ADDED_MISSING@mx.google.com>
2020-08-27 6:56 ` Kehuan Feng
[not found] ` <20200827125747.5816-1-hdanton@sina.com>
2020-08-28 1:45 ` Kehuan Feng
2020-09-03 5:01 ` Cong Wang
2020-09-03 8:39 ` Paolo Abeni
2020-09-03 17:43 ` Cong Wang
2020-09-04 5:07 ` John Fastabend
2020-09-10 20:15 ` Cong Wang
2020-09-10 21:07 ` John Fastabend
2020-09-10 21:40 ` Paolo Abeni
2021-04-02 19:25 ` Jiri Kosina
2021-04-02 19:33 ` Josh Hunt
[not found] ` <20210403003537.2032-1-hdanton@sina.com>
2021-04-03 12:23 ` Jiri Kosina
2021-04-06 0:55 ` Yunsheng Lin
2021-04-06 7:06 ` Michal Kubecek
2021-04-06 10:13 ` Juergen Gross
2021-04-06 12:17 ` Yunsheng Lin
2021-04-06 1:49 ` Cong Wang
2021-04-06 2:46 ` Yunsheng Lin
2021-04-06 7:31 ` Michal Kubecek
2021-04-06 12:24 ` Yunsheng Lin
[not found] ` <20200903101957.428-1-hdanton@sina.com>
2020-09-04 3:20 ` Kehuan Feng
2020-09-10 20:19 ` Cong Wang
2020-09-14 2:10 ` Yunsheng Lin
2020-09-17 19:52 ` Cong Wang
2020-09-18 2:06 ` Kehuan Feng
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