..
  Copyright 2022 Max Planck Institute for Software Systems, and
  National University of Singapore
..
  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:
..
  The above copyright notice and this permission notice shall be
  included in all copies or substantial portions of the Software.
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  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

###################################
Troubleshooting / FAQ
###################################

This is a collection of common troubleshooting tips and answers to frequently
asked questions.


.. _sec-troubleshoot-getting-help:

******************************
Getting Help
******************************

We love to hear from you. If you have questions, want to discuss an idea, or
encountered issues while using SimBricks, we are available on `Slack
<https://join.slack.com/t/simbricks/shared_invite/zt-16y96155y-xspnVcm18EUkbUHDcSVonA>`_
for quick answers and interactive discussions. If you find bugs or want to
request a feature, feel free to open an `issue on GitHub
<https://github.com/simbricks/simbricks/issues>`_.


.. _sec-convert-qcow-images-to-raw:

*****************************************
Error Opening images/output-base/base.raw
*****************************************

Some of our host simulators, e.g., gem5 and Simics, require raw disk images. If
these aren't available, you will see the error in the title or something
similar. If you use our Docker images, we deliberately remove these since Docker
doesn't handle large, sparse files well, which leads to large Docker image
sizes. We include disk images in the qcow format though, which can easily be
converted to raw. To do so, just run the following (requires QEMU to be built
first):

.. code-block:: bash

  $ make convert-images-raw

If you are not using the provided docker containers, you might need to build the
qcow images by running the following (again, requires QEMU to be built first):

.. code-block:: bash

  $ make build-images-min

.. _sec-gem5-perf:

*********************************
gem5 Panic PerfKvmCounter::attach
*********************************

gem5 needs access to the syscall ``perf_event_open``. To allow access,
``/proc/sys/kernel/perf_event_paranoid`` has to be set to 1 or lower on the host
system. You can check the current value with

.. code-block:: bash

  $ cat /proc/sys/kernel/perf_event_paranoid

To change the setting, use this command:

.. code-block:: bash

  $ sudo sysctl -w kernel.perf_event_paranoid=1

If you are using SimBricks from within a Docker container, you also need to
start the container with the parameter ``--privileged`` for the
``perf_event_open`` syscall to be accessible. Our VS Code dev container is
configured to already do so, just start it as usual from within VS Code and you
are good to go. Otherwise, add the parameter to your ``docker run`` command.

************************************
Is My Simulation Stuck or Just Slow?
************************************

It is possible to check the current timestamp of individual component
simulators. If the timestamp of a simulator which is synchronizing with at least
one other simulator isn't advancing, the whole simulation is stuck. Many of our
component simulators print their timestamp when you send them a USR1 signal, for
example, by running ``kill -s USR1 <insert_pid_of_simulator>``. By doing this
multiple times, you can check whether the timestamp advances.

If you invoked the orchestration framework in verbose mode (see
:ref:`sec-command-line`), the current timestamp is printed directly in the
terminal. If not then you have to stop the experiment via Ctrl+C to produce
the output JSON file. All the simulators' output is logged
there.

************************************
Understanding Simulation Performance
************************************
