Re: Packet gets stuck in NOLOCK pfifo_fast qdisc
From: Cong Wang <hidden>
Date: 2020-09-10 20:19:40
Also in:
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Possibly related (same subject, not in this thread)
- 2021-04-06 · Re: Packet gets stuck in NOLOCK pfifo_fast qdisc · Yunsheng Lin <hidden>
- 2021-04-06 · Re: Packet gets stuck in NOLOCK pfifo_fast qdisc · Yunsheng Lin <hidden>
- 2021-04-06 · Re: Packet gets stuck in NOLOCK pfifo_fast qdisc · Juergen Gross <jgross@suse.com>
- 2021-04-06 · Re: Packet gets stuck in NOLOCK pfifo_fast qdisc · Michal Kubecek <hidden>
- 2021-04-06 · Re: Packet gets stuck in NOLOCK pfifo_fast qdisc · Michal Kubecek <hidden>
On Thu, Sep 3, 2020 at 8:21 PM Kehuan Feng [off-list ref] wrote:
I also tried Cong's patch (shown below on my tree) and it could avoid the issue (stressing for 30 minutus for three times and not jitter observed).
Thanks for verifying it!
quoted hunk ↗ jump to hunk
--- ./include/net/sch_generic.h.orig 2020-08-21 15:13:51.787952710 +0800 +++ ./include/net/sch_generic.h 2020-09-03 21:36:11.468383738 +0800@@ -127,8 +127,7 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc) { if (qdisc->flags & TCQ_F_NOLOCK) { - if (!spin_trylock(&qdisc->seqlock)) - return false; + spin_lock(&qdisc->seqlock); } else if (qdisc_is_running(qdisc)) { return false; }I am not actually know what you are discussing above. It seems to me that Cong's patch is similar as disabling lockless feature.
From performance's perspective, yeah. Did you see any performance downgrade with my patch applied? It would be great if you can compare it with removing NOLOCK. And if the performance is as bad as no NOLOCK, then we can remove the NOLOCK bit for pfifo_fast, at least for now. Thanks.