Supervisor

Past activities in optimizing the performance of the HotSpotTM Java Virtual Machine focused on the performance of the dynamic compilers and the supporting runtime. Since dynamically compiled code is stored in a code cache to avoid recompilations, the organization and maintenance of the code cache has a significant impact on the overall performance. The organization of the code cache became even more important with the introduction of tiered compilation in Java Platform, Standard Edition (Java SE) 7. By using two dynamic compilers with different characteristics, not only the amount, but also the number of different types of compiled code increased. The current code cache is optimized to handle homogeneous code, i.e., only one type of compiled code. The code cache is organized as a single heap data structure on top of a contiguous chunk of memory. Therefore, profiled code which has a predefined limited lifetime is mixed with non-profiled code, which potentially remains in the code cache forever. This leads to different performance and design problems. For example, the method sweeper has to scan the entire code cache while sweeping, even if some entries are never flushed or contain non-method code. This thesis addresses these issues at a lower layer by redesigning the structure of the code cache