Deconstructing the LuaJIT Pseudo Memory Leak

Summary

When managing large-scale, high-concurrency OpenResty/LuaJIT services, many seasoned architects have encountered a perplexing and counter-intuitive challenge: while the service’s business logic operates robustly and Lua VM-level garbage collection (GC) data indicates normal operation, operating system monitoring tools consistently show an irreversible, continuous increase in the process’s Resident Set Size (RSS). This peculiar phenomenon, an apparent “leak” that isn’t a logical one, often looms as a Damocles sword over production environments. Ultimately, it leads to containers being forcibly terminated due to Out of Memory (OOM) errors, introducing unpredictable risks to online services striving for ultimate stability.For a long time, engineering teams have attempted to mitigate this persistent issue by merely adjusting GC parameters or scaling resources. However, these measures often prove superficial, failing to address the core problem. This isn’t simply a code quality issue; rather, it stems from a “communication gap” between the runtime memory allocation mechanism and the operating system. LuaJIT-plus is our definitive solution to this fundamental challenge.It is not merely a patch, but an enhanced runtime environment equipped with proactive memory reclamation capabilities. Its design aims to fundamentally overcome the “allocate-only” limitation of LuaJIT’s default allocator, thereby eradicating the problem of artificially inflated RSS caused by memory fragmentation. This article will delve into the technical principles behind this phenomenon and explain how LuaJIT-plus, by rethinking memory management strategies, transforms an unpredictable resource consumption into a healthy, predictable, and “breathing” memory model.In the architectural design of high-performance network services, technology stacks built on OpenResty or native LuaJIT have consistently been the go-to solutions for handling high traffic volumes, thanks to their exceptional concurrent processi...