  Driven by the visions of Internet of Things and 5G communications, the edge
computing systems integrate computing, storage and network resources at the
edge of the network to provide computing infrastructure, enabling developers to
quickly develop and deploy edge applications. Nowadays the edge computing
systems have received widespread attention in both industry and academia. To
explore new research opportunities and assist users in selecting suitable edge
computing systems for specific applications, this survey paper provides a
comprehensive overview of the existing edge computing systems and introduces
representative projects. A comparison of open source tools is presented
according to their applicability. Finally, we highlight energy efficiency and
deep learning optimization of edge computing systems. Open issues for analyzing
and designing an edge computing system are also studied in this survey.
