A side effect of a fully configurable system is that it is just about impossible to answer questions like "What is the memory footprint of the kernel?" or "What is the interrupt latency?" These figures depend in large part on the configuration options selected by the user. For example if a simple application does not require the kernel at all, directly or indirectly, then the kernel package can be disabled completely and its memory footprint is 0 bytes.

Basic performance characterization data is available as part of the documentation as part of the architecture specific Getting Started manual, together with a description of the tests that were used to obtain this data. The sources for these tests are included with the eCos distribution.