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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | SEE ALSO | AUTHOR | RESOURCES | COPYING | NOTES | COLOPHON |
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TRACE-CMD-ATTACH(1) libtracefs Manual TRACE-CMD-ATTACH(1)
trace-cmd-attach - attach a guest trace.dat file to a host
trace.dat file
trace-cmd attach [OPTIONS] host-trace-file guest-trace-file
guest-pid [guest-pid ...]
The trace-cmd(1) attach is used to take a trace.dat file created
on a guest and attach it to a trace.dat file that was created on
the host. In most cases, trace-cmd-agent(1) can be used to
automate this, but if for some reason, the agent isn’t
appropriate, it may be required to start trace-cmd recording on
the guest with trace-cmd-record(1). If the host recording is
activated at the same time, one can use trace-cmd attach(1) to
connect the guest and host files as if they were created by the
trace-cmd agent.
host-trace-file
The trace.dat file created by the host. Must have kvm_exit
and kvm_entry events, and use the "tsc2nsec" clock.
guest-trace-file
The trace.dat file created by the guest. Must use the
"x86-tsc" clock. For now, this is only supported on x86, it
may support other achitectures later.
guest-pid
The process ID of the host thread that represents the guests
threads. Each process ID that represents all of the guest
vCPUs should be listed. Note, you can add more than just the
threads that represent the guest vCPUs, as the tool will
search the host-trace-file for kvm_exit and kvm_entry events
to match these PIDs with the vCPUs that they represent.
-c cpus
Specify a the number of CPUS the guest has.
-s timeshift
A comma separated list of the format
offset,scale,frac,timestamp These values map to what are
given in /sys/kernel/kvm/<pid>/vcpu/*
*offset*: Is the offset of the guest. "tsc-offest" in the directory. Note
that the value listed here is the negative of what is listed in
the directory.
*scale*: The scaling factor. "tsc-scaling-ratio"
*frac*: The fraction bits. "tsc-scaling-ratio-frac-bits"
*timestamp*: The timestamp to start using the above. In some cases, the
values may change over time. By adding a timestamp, it will
take effect after the timestamp has been hit. Normally
this would be zero.
Currently, only one timeshift is given per CPU. One *-s* option should be
given for each CPU. If there are less options than CPUs, then the last option
given will be used for the rest of the CPUs. If only one option is given, then
the values for that option will be used for all CPUs.
Enable all events for tracing:
$ # find the process for a given guest
$ ps aux |grep qemu
libvirt+ 63170 5.6 1.6 13994848 4257540 ? Sl May02 2884:49 /usr/bin/qemu-system-x86_64...
$ # Use 63170 to find all the PIDs for the give guest
$ ls /proc/63170/task
1541591 63170 63198 63209 63211 63213 63214 63215 63216 63217 63218 63219 63234
$ # Find the tsc offset
$ su
# cat /sys/kernel/debug/kvm/63170-15/vcpu0/tsc-offset
-27950965013436847
# trace-cmd record -C tsc2nesc -e kvm -e sched -e irq -e timer
# on guest:
# trace-cmd record -C x86-tsc -e sched -e irq -e timer sleep 10
# back on host, hit Ctrl^C to stop tracing after the guest is done
# # Make the trace.dat user owned by your user account.
# chown user.user trace.dat
# exit
$ scp root@guest:trace.dat trace-guest.dat
$ # now attach the two files (guest has 8 CPUs)
$ trace-cmd attach -c 8 -s 27950965013436847 trace.dat trace-guest.dat 1541591 63170 63198 63209 63211 63213 63214 63215 63216 63217 63218 63219 63234
$ trace-cmd report -i trace.dat -i trace-guest.dat
$ # now you should see the guest trace interleaved within the host trace.
trace-cmd(1), trace-cmd-report(1), trace-cmd-start(1),
trace-cmd-stop(1), trace-cmd-extract(1), trace-cmd-reset(1),
trace-cmd-split(1), trace-cmd-list(1), trace-cmd-listen(1),
trace-cmd-profile(1)
Written by Steven Rostedt (Google) <rostedt@goodmis.org[1]>
https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/
Copyright (C) 2010 Red Hat, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
This page is part of the trace-cmd (a front-end for Ftrace)
project. Information about the project can be found at
⟨https://www.trace-cmd.org/⟩. If you have a bug report for this
manual page, see ⟨https://www.trace-cmd.org/⟩. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git⟩ on
2023-12-22. (At that time, the date of the most recent commit
that was found in the repository was 2023-11-28.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
libtracefs 09/24/2023 TRACE-CMD-ATTACH(1)
Pages that refer to this page: trace-cmd(1)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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