When adding more threads adds more problems - Thread-sharing between elements in GStreamer.

In GStreamer we liberally use threads everywhere: for parallelizing processing on multiple cores, for decoupling processing of different pipeline parts, for timers and for blocking operations. A normal GStreamer pipeline can easily have dozens of threads interacting with each other.

In this presentation the topic is not that using threads is hard and about all the thread-safety problems that potentially exist: by the design of GStreamer this is relatively well-handled already.

Instead the topic is the bad scalability of using a new thread for everything. If every pipeline you create uses 10 threads, and you'd like to run 100s of them on the same machine, you can easily end up using all your system resources (both CPU and memory) just for these threads while not being able to do the actual data processing fast enough or in time.

An experimental set of GStreamer elements will be introduced to show a potential solution to this problem for specific use-cases by sharing a fixed number of threads between different elements, and similar approaches to other existing elements (e.g. the RTP jitterbuffer).

Afterwards results of that approach in one specific scenario will be presented, and in the end potential future development will be discussed and what could be changed in GStreamer core for 2.0 to integrate such approaches in a cleaner and lower-overhead way to make GStreamer more scalable.

Sebastian Dröge (slomo) is a Free Software developer and one of the GStreamer maintainers and core developers. He has been involved with the project since more than 10 years now. He also contributes to various other Free Software projects, like Debian, Rust, GNOME and WebKit. While finishing his master's degree in computer sciences at the University of Paderborn in Germany, he started working as a contractor for GStreamer and related technologies. Sebastian is one of the founders of Centricular, a company providing consultancy services, where he's working from his new home in Greece on improving GStreamer and the Free Software ecosystem in general.

Apart from multimedia related topics, Sebastian has an interest in digital signal processing, programming languages, machine learning, network protocols and distributed systems.