seL4 Profiler

This is a framework for profiling on-top of seL4. It is a statistical profiler that can be configured to sample based on different events and frequencies. There is a sample client that can dump packets either over serial or the network.

Currently, we support armv8 platforms. Specifically, we have tested on the maaxboard and odroidc4. The profiler component should be SoC agnostic, however, the client is reliant on the current seL4 sDDF development.

Project Status

Currently completed items:

• PMU interface for arm8.
• Kernel changes to record sample data (instruction pointer, callstack).
• Statistical profiler.
• Client to send samples over serial/ethernet.
• Using protocol buffers to send data over ethernet.
• Conversion tool to generate perf.data files.

TO-DO:

• Multicore support. A development branch exists at multicore.

Installation

• We require a special kernel configuration. The kernel version can be found at: https://github.com/Kswin01/seL4/tree/microkit-dev.
• We have tested with this version of Microkit: https://github.com/Kswin01/sel4cp/tree/microkit_prof_dev.

Building example

• Ensure that you have either downloaded the appropriate Microkit SDK, or built from source. Instructions for building Microkit can be found in the Microkit repo.
• Please check the example directory for build instructions.

Protocol Buffers

We use protocol buffers to encode our samples. Within the profiler tool, we use nanopb. If you wish to modify the proto structure, please find the pmu_sample.proto file in the protobuf/ directory at the root of the repository.

There are two parts to protobuf in the repository.

1. Within the profiler itself, in order to encode sample data.
2. Within the netconn utility in order to parse and decode the sample data.

Generating nanopb files

We use version 0.4.8 of nanopb, you can find the releases here.

For example, to reproduce the nanopb generated files on Linux:

# In the root of the repository
wget https://jpa.kapsi.fi/nanopb/download/nanopb-0.4.8-linux-x86.tar.gz
tar xf nanopb-0.4.8-linux-x86.tar.gz
nanopb-0.4.8-linux-x86/generator-bin/protoc --nanopb_out=. protobuf/pmu_sample.proto

Generating Python protobuf files

Please ensure that you have installed the Google Protocol Buffer compiler. More information can be found here.

You can install this using pip with the following command: pip install protobuf.

# In the root of the repository
protoc --python_out=protobuf/python --proto_path=protobuf/python protobuf/python/pmu_sample.proto

Notes

• This system currently requires a Python client to be connected to the board over the network. The client can be found within the netconn directory. Instructions can be found in netconn/README.md.

• This demo system is integrated with the sDDF. Driver support will be inline with sDDF development.

• Additionally, found within the toperf directory is a tool to convert from the samples file outputted by the netconn tool to a perf.data file. This will allow us make use of existing infrastructure surrounding perf, such as perf report and flamegraph tools such as Mozilla Profiler.

Demo System

A demo system can be found in the example directory. This includes a TCP echo server as well as two background dummy programs. This demo system is for the odroidc4 and maaxboard platforms.

How to use

Controlling the profiler

In the include/config.h file, there is a #define called CLIENT_CONFIG. Set this value to whatever control method that you wish to use. 0 is using serial, 1 is using the network controller.

Serial Control

• Using this profiler over serial will result in the raw json samples being dumped to terminal.
• You can enter the following values into the terminal with the multiplexer set to hand characters to the profiler:
  • 1 - Start profiling
  • 2 - Stop profiling, dump all packets

This works on the odroidc4 and maaxboard. Ensure that the Makefile is changed appropriately, and the right MMIO addresses and IRQ's are used in the system description.

Network Control

More details can be found in the netconn directory.

Converting to Perf

The serial control will output the raw JSON samples. The netconn tool will output the correctly formatted JSON file. Please see the toperf/ directory for more information on using the toperf tool.