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  1. JikesRVM
  2. RVM-399

Separate Heap For VM objects

    Details

    • Type: Improvement
    • Status: Open
    • Priority: Medium
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: 1000
    • Component/s: MMTk, Runtime
    • Labels:
      None

      Description

      In most JVMs there is no confusion between memory allocated for the application and memory allocated by the running of the VM itself (for example a call to malloc() within the JIT). However, in Jikes RVM, the VM and the application are both written in Java. Moreover, they currently share the same heap. It would be very desirable to improve this situation and separately allocate VM and application objects. Aside from cleaner accounting and behaving more like a production JVM, there may be opportunities for performance optimizations since the lifetimes of objects created by the JIT will typically be bounded by the invocation of a single compilation, as an example.

      This project would start by identifying all transitions from the application into the VM proper and channeling all such transitions through a zero-cost "trap", which simply serves as a marker. The trap can be viewed as analogous to a kernel trap in the OS setting. The project would also involve writing a simple checking routine which would walk the stack and determine whether execution was currently within the VM or application context. The combination of these mechanisms could then be used to identify and verify all application<->VM transitions.

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              • Assignee:
                Unassigned
                Reporter:
                ianrogers Ian Rogers
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                • Created:
                  Updated: