Tock binary size - Blog - Tweede golf
A lot of code size bloat. In 2018, when Tock was first released, a minimal kernel required ~7KB for code. Today, the default build for most platforms is easily over 100KB. This is a big problem for resource-sensitive applications--where a platform may only have a couple 100KB of executable flash or must execute from memory.
We recently worked on a project that explores where all of this extra code size is spent, how much of it is fundamental to the design of Tock, and how Tock could adapt to support more platforms with stricter code size constraints.
Let's first establish a baseline. We pick the NRF52840DK, a development board for the popular NRF52840 from Nordic Semiconductors. It is one of the main development boards in the Tock community and is pretty representative of many embedded applications. It helps that we also happened to have a few lying around. Our exploration is based off of a recent tip-version of Tock (commit 41aafdca37e6961af3ae19742edcdf40cd8e8d1a). The total size of the kernel for this version is
OK, most of that 200KB is from peripheral drivers, including a full 6lowpan/802.15.4 stack, Bluetooth, as well as a number of subsystems for debugging, like a process console. Because Tock separates the kernel from applications, which can be loaded dynamically, the drivers a board configures are compiled in regardless of whether any application actually ever uses them.
