TRACE-CMD-ATTACH(1) | libtracefs Manual | TRACE-CMD-ATTACH(1) |
NAME¶
trace-cmd-attach - attach a guest trace.dat file to a host trace.dat file
SYNOPSIS¶
trace-cmd attach [OPTIONS] host-trace-file guest-trace-file guest-pid [guest-pid ...]
DESCRIPTION¶
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
guest-trace-file
guest-pid
OPTIONS¶
-c cpus
-s timeshift
*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.
EXAMPLES¶
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.
SEE ALSO¶
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)
AUTHOR¶
Written by Steven Rostedt (Google) <rostedt@goodmis.org[1]>
RESOURCES¶
https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/
COPYING¶
Copyright (C) 2010 Red Hat, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).
NOTES¶
- 1.
- rostedt@goodmis.org
02/10/2024 | libtracefs |