Profiling #

In order to determine and analyse the performance of a LionsOS system, we need a systematic way of recording where CPU time is spent.

We achieve this with a statistical profiler, which means that we take regular samples of the Performance Monitor Unit (PMU) hardware to determine how much CPU time a particular Protection Domain (PD) is using.

Availability #

All the work relating to profiling support can be found here.

While it is functional and receiving internal use to profile our systems, it is yet to be properly integrated with LionsOS. However, getting it integrated is a priority for us.

Architecture #

When you profile a system in LionsOS, there are two extra components involved. There is the PMU driver itself which manages and controls the PMU hardware and publishes sample data via shared memory. This data is then consumed by a client that sends the data over the chosen transport.

The transfer of sampling data happens over the standard interfaces of LionsOS’ I/O. It is up to the system designer to configure how they want to transfer the sampling data, right now we have this working for serial and ethernet devices. This sampling data is recorded by a simple script that is run on the host system (e.g the developer’s machine).