If you turn on the main loop dispatch event logs and look at the results in the g2 viewer [or dump them in ascii] you can make pretty accurate lap time estimates for any workload. Roughly speaking, packets take 1 lap time to arrive and then leave.
The “circuit-node <node-name>” game produces one elog event per frame, so you can look at several million frame circuit times. Individually timestamping packets would be more precise, but calling clib_cpu_time_now(...) (rdtsc instrs on x86_64) twice per packet would almost certainly affect forwarding performance. See https://fd.io/docs/vpp/master/gettingstarted/developers/eventviewer.html /*? * Control event logging of api, cli, and thread barrier events * With no arguments, displays the current trace status. * Name the event groups you wish to trace or stop tracing. * * @cliexpar * @clistart * elog trace api cli barrier * elog trace api cli barrier disable * elog trace dispatch * elog trace circuit-node ethernet-input * elog trace * @cliend * @cliexcmd{elog trace [api][cli][barrier][disable]} ?*/ /* *INDENT-OFF* */ From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Christian Hopps Sent: Saturday, April 18, 2020 3:14 PM To: vpp-dev <vpp-dev@lists.fd.io> Cc: Christian Hopps <cho...@chopps.org> Subject: [vpp-dev] Packet processing time. The recent discussion on reference counting and barrier timing has got me interested in packet processing time. I realize there's a way to use "show runtime" along with knowledge of the arc a packet follows, but I'm curious if something more straight-forward has been attempted where packets are timestamped on ingress (or creation) and stats are collected on egress (transmission)? I also have an unrelated interest in hooking into the graph immediate-post-transmission -- I'd like to adjust an input queue size only when the packet that enqueued on it is actually transmitted on the wire, and not just handed off downstream on the arc -- this would be a likely the same place packet stat collection might occur. :) Thanks, Chris.
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