ZGC Root Scanning
Erik Österlund · 2026
Root scanning is an important part of tracing. These are the initial edges from outside of the heap into the heap, where tracing starts. Identifying root objects for the tracing has classically been performed as part of a GC pause when the world is stopped. However, ZGC performs this operation in a concurrent phase, while the application is running. This chapter describes how that is done by ZGC in more detail.