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https://github.com/xdp-project/bpf-examples.git
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b84b89dc4b
Also found measurement tool can disturb timing. I might have to write this in BPF-C directly to avoid overhead. Signed-off-by: Jesper D. Brouer <netoptimizer@brouer.com>
79 lines
1.8 KiB
Plaintext
Executable File
79 lines
1.8 KiB
Plaintext
Executable File
#!/usr/local/bin/bpftrace
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#include <linux/skbuff.h>
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// tracepoint:net:net_dev_start_xmit
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tracepoint:net:net_dev_xmit
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{
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$skb = (struct sk_buff *)args->skbaddr;
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//$tstamp = (uint64)$skb->tstamp;
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$tstamp = $skb->skb_mstamp_ns;
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$now = nsecs;
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// if ($skb->mark > 0) {
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if ($tstamp > 0) {
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if ($now >= $tstamp) {
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$diff_late = $now - $tstamp;
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} else {
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$diff_ahead = $tstamp - $now;
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}
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@tstamp_usec_diff_late = hist($diff_late / 1000);
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@tstamp_usec_diff_ahead = hist($diff_ahead / 1000);
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}
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/* Capture burstiness over a time period, by dividing nanosec
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* timestamp with wanted period, and keeping state byte counter as
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* long as timestamp match.
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*
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* Practical usage shows that bpftrace uses a hash-map to implement
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* this, which unfortunately cost too much (shows 5% jhash cpu
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* usage), enough overhead to change behavior of prod system.
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*/
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//$period = $now / 10000; /* 10000 = 10 usec */
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$period = $now / 30000; /* 30000 = 30 usec */
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if (@state[cpu] == $period) {
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@state_bytes[cpu] += $skb->len;
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} else {
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@state[cpu] = $period;
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if (@state_bytes[cpu] > 0) {
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@byte_burst[cpu] = hist(@state_bytes[cpu]);
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}
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@state_bytes[cpu] = $skb->len; /* Reset counter */
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}
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}
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/*
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tracepoint:qdisc:qdisc_dequeue
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{
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@qdisc_bulk_dequeue = lhist(args->packets, 0,64,1);
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}
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*/
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/*
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kretfunc:dev_hard_start_xmit
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{
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// Wanted to know if ret == NETDEV_TX_BUSY
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# ERROR: kfunc/kretfunc not available for your linked against bcc version.
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}
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*/
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/* How often does FQ-pacer find no-packets are qualified to be
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* scheduled, which leads to scheduling an hrtimer event, that will
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* start qdisc again at a later time.
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*
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* We cannot kprobe fq_dequeue as it is a module.
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*/
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/*
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kprobe:qdisc_watchdog_schedule_range_ns
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{
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@qdisc_watchdog[cpu] = count();
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}
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kprobe:__netif_schedule
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{
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@__netif_schedule[cpu] = count();
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}
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*/
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