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From: Prasad Pandit <>
To: Steven Rostedt <>
Cc: Daniel Bristot de Oliveira <>,
Subject: Re: About tracing clues
Date: Sat, 20 Aug 2022 14:51:02 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <20220819135047.45243742@gandalf.local.home>

Hello Steven,

On Fri, 19 Aug 2022 at 23:29, Steven Rostedt <> wrote:
> Hmm you need to turn off line wraps when pasting in output like this.
> Because the line wraps make it very difficult to follow.

* True, I should've done that; I'll remember to do it.

> To get the vsocket CID id, you can run the agent:
>   # trace-cmd agent
> listening on @3:823
> The @3 is the CID (823 is the port).
> Hit Ctrl-C on to kill the agent.
> Then on the host, run:
>  # trace-cmd agent -P 3
> Where 3 is the CID of the guest you want to connect the host (the same
> number from the 'trace-cmd agent'. That is, if it was @4:823, then use
> '-P 4'). The host agent above should also have a:
>  listening on @2:823
> or something. You'll need the host's CID too.
> Then on the guest, run:
> [ You do not need -p nop if you have -e used ]
>   # trace-cmd record --poll -M 1E -e all --proxy 2 --name host -e kvm -e sched -e irq /home/test/rt-tests/oslat --cpu-list 1-4 --rtprio 1 --duration 12h -T 30 oslat V 2.30
> And then when it ends, you'll have two files. One that is trace.dat and one
> that is trace-host.dat. If everything worked well, the two would also be in
> sync with each other. Doing:
>   # trace-cmd report -i trace-host.dat -i trace.dat
> Will show the host events happening with the guest events. If the host
> caused the latency, you will definitely see it.
> If you have the latest kernelshark, you can run:
>   kernelshark trace-host.dat -a trace.dat
> And then select "Plots" -> "KVM Combo Plots" and in the popup, select the
> box for "all".
> Then you'll see plots for each virtual CPU and the host thread that represents it.

* I see, thank you so much for these interesting details. I'll try
these steps and get back to you soon.

Thank you.
  - P J P

  reply	other threads:[~2022-08-20  9:21 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-19 10:06 About tracing clues Prasad Pandit
2022-08-19 17:50 ` Steven Rostedt
2022-08-20  9:21   ` Prasad Pandit [this message]
2022-08-23 19:24     ` Prasad Pandit
2022-08-23 19:30       ` Steven Rostedt

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