Re: [Qemu-devel] [PATCH] kvm: add flightrecorder script

[Avi Kivity <avi@redhat.com>]

On 03/09/2012 04:13 PM, Stefan Hajnoczi wrote:
> The kvm kernel module includes a number of trace events which can be
> useful when debugging system behavior.  Even on production systems these
> trace events can be used to observe guest behavior and identify the
> source of problems.
>
> The kvm_flightrecorder script is a command-line wrapper for the
> /sys/kernel/debug/tracing interface.  Kernel symbols do not need to be
> installed.
>
> This script captures a fixed-size buffer of KVM trace events.  Recent
> events overwrite the oldest events when the buffer size is exceeded and
> it is possible to leave KVM tracing enabled for any period of time with
> just a fixed-size buffer.  If the buffer is large enough this script is
> a useful tool for collecting detailed information after an issue occurs
> with a guest.  Hence the name "flight recorder".
>
> The script can also be used in 'tail' mode to simply view KVM trace
> events as they occur.  This is handy for development and to ensure that
> the guest is indeed running.
>
>

Have you considered updating trace-cmd or perf-something instead?  While
each of these tools are useful we miss out on combining capabilities. 
For example you could 'perf probe' a dynamic tracepoint and flightrecord
it together with kvm tracepoints.

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