Abstract Object and Native Code Thread Mobility

We present a technique for moving objects and threads among het-erogeneous computers at the native code level. To enable mobility of threads running native code, we convert thread states among machine-dependent and machine-independent formats. We introduce the concept of bLts stops, which are machine-independent representations of program points as represented by program counter values, The concept of bus stops can be used also for other purposes, <~. g., to aid inspecting and debugging optimized code, garbage collection e~c. We also discuss techniques for thread mobility among processors executing differently optimized codes. We demonsti-ate the viabi lily of our ideas by providing a prototype implementation ot ’ object and thread mobility among heterogWCOUS computers, The prototype uses the Emerald distributed progt-amming language without modification; we have merely ex-tended the Emerald runtime system and the code generator of the Emerald compiler. Our extensions allow object and thread mobility among VAX, Sun-3, HP9000/300, and Sun SPARC workstations. The excellent intra-node performance of the original homogeneous Emerald is retained: migrated threads run at native code speed bet’ore and after migration; the same speed as on homogeneous Emer-alci and close to C code performance. Our implementation of mobility hm not been optimized: thread mobility and trans-architecture invocations take about 60 % longer than in lhe homogeneous imple-mentation. We believe this is the first implementation of full object and [hrcad mobility among heterogeneous computers with threads exe-cu(ing native code.