netdev - Re: packet stuck in qdisc

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Date:   Thu, 14 Apr 2022 11:05:14 +0800
From:   Guoju Fang <gjfang@...ux.alibaba.com>
To:     vray@...rayinc.com
Cc:     davem@...emloft.net, guoju.fgj@...baba-inc.com, kuba@...nel.org,
        linyunsheng@...wei.com, netdev@...r.kernel.org,
        sjones@...rayinc.com, vladimir.oltean@....com
Subject: Re: packet stuck in qdisc

Hi Vincent,

I use the following bpftrace code to print those skb that exceed a 
latency (10ms). Plese see if it can help you.


#!/usr/bin/bpftrace

tracepoint:net:net_dev_queue
{
	@start[args->skbaddr] = nsecs;
	@core[args->skbaddr] = cpu;
}

tracepoint:net:net_dev_start_xmit
{
	$lat = (nsecs - @start[args->skbaddr]) / 1000;
	if ($lat > 10000) {
		time("%H:%M:%S  ");
		printf("queue core %d, xmit core %d, len %d, lat %d us\n",
			@core[args->skbaddr], cpu, args->len, $lat);
	}
	delete(@start[args->skbaddr]);
	delete(@core[args->skbaddr]);
}


Best Regards,
Guoju.