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Re: Performance measurement

From: sterbl . ta
Subject: Re: Performance measurement
Date: Thu, 2 Apr 2020 21:21:10 +0200 (CEST)

Placing "sleep 3" before qemu-system-x86_64 command as suggested fixes the problem. Thank you once again for your kindly help, most appreciate it!

Apr 2, 2020, 09:57 by address@hidden:
On Thu, Apr 02, 2020 at 11:33:42AM +0200, address@hidden wrote:
Dear Stefano,

First thank you for providing the script. It's really useful!

You're welcome! I'm happy that it could be useful :-)

I executed the commands in prerequisite section before running the perf script, and its output as below

$ cat  /sys/kernel/debug/tracing/events/kvm/enable
$ cat /proc/sys/kernel/perf_event_paranoid
$ ls -ld /sys/kernel/debug
drwxr-xr-x 40 root root 0 Apr  1 21:25 /sys/kernel/debug
$ ls -ld /sys/kernel/debug/tracing
drwxr-xr-x 6 root root 0 Apr  1 21:25 /sys/kernel/debug/tracing

The size of qemu_perf.data is around 74M (can't be attached), so I put it in the link https://drive.google.com/file/d/14d0PATAK9ldep65aJ4D-SgBImVIO_cjc/view?usp=sharing

looking at your data (perf script -i qemu_perf.data), seems that the
'sched_process_exec' event is not recorded and it usually happens because
'perf record' takes some time to initialize before starting record.

So you can put a 'sleep 3' before you start QEMU as a workaround (maybe I
should update the README in the repository...)
And below is the script used to generate the qemu_perf.data (After executing this script, the vm was started, I login then execute shutdown command `sudo shutdown -Ph now` to return back to the command prompt.

# Start perf record to get the trace events
perf record -a -e kvm:kvm_entry -e kvm:kvm_pio -e sched:sched_process_exec \
            -o $PERF_DATA &

# Wait some seconds to have perf record ready
sleep 3

qemu-system-x86_64 -enable-kvm \
    -drive "file=disk.img,if=virtio" -drive "file=seed.img,if=virtio,format=raw"  \
    -device virtio-net-pci,netdev=net00 --netdev type=user,id=net00 \
    -m 512 -nographic

# Stop perf record
kill $PERF_PID

# Get the measurements
perf script -s qemu-boot-time/perf-script/qemu-perf-script.py -i $PERF_DATA

Also the script got executed and it output (error) is as follow:

$ perf script -s qemu-boot-time/perf-script/qemu-perf-script.py -i qemu_perf.data
in trace_begin
Traceback (most recent call last):
  File "qemu-boot-time/perf-script/qemu-perf-script.py", line 195, in kvm__kvm_entry
    if (events.traces[pid].qemu_init_end != 0):
AttributeError: 'collections.defaultdict' object has no attribute 'qemu_init_end'
Fatal Python error: problem in Python trace event handler

Current thread 0x00007f41bdc5d800 (most recent call first):

Thank you again for your help!

Let me now if this helps!


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