On Tue, 17 Feb 2026 22:43:47 GMT, Chad Rakoczy <[email protected]> wrote:
>> [JDK-8374045](https://bugs.openjdk.org/browse/JDK-8374045) >> >> This PR adds a new utility tool CodeCacheFragmenter to help with testing >> HotSpot code cache fragmentation scenarios. The tool is a Java agent that >> uses the WhiteBox API to create and randomly free dummy code blobs in the >> NonProfiled code heap to achieve a specified fill percentage. It includes >> configurable parameters for blob sizes, target fill percentage (0-100%), and >> random seeding to enable reproducible fragmentation patterns. The utility is >> built via a standard Makefile and produces `codecachefragmenter.jar` which >> can be used as a Java agent with `-javaagent` flag. This tool is intended >> for performance testing and experimentation with code cache behavior under >> various fragmentation conditions. The distribution of blob sizes aims to >> represent real world nmethod sizes which are based on sizes from running >> Renaissance benchmarks. >> >> This is useful to show the performance benefits of >> [JDK-8326205](https://bugs.openjdk.org/browse/JDK-8326205) >> >> Distribution of nmethod size from Renaissance benchmarks: >> <img width="3570" height="1766" alt="renaissance_dis" >> src="https://github.com/user-attachments/assets/cde9645a-38d3-4506-811f-646ced78715a"; >> /> >> >> Distribution of dummy blob size from CodeCacheFragmenter: >> <img width="3570" height="1766" alt="frag_new_dis" >> src="https://github.com/user-attachments/assets/2c61cc0d-20a8-4ae0-af42-8cfc98271217"; >> /> > > Chad Rakoczy has updated the pull request incrementally with one additional > commit since the last revision: > > Update rng Update random number generation for blob size to be more representative of real world workloads. Renaissance benchmarks: <img width="3570" height="1766" alt="renaissance_dis" src="https://github.com/user-attachments/assets/92530794-725a-4b4a-b3cc-0c7c7d282bfb"; /> Old: <img width="3570" height="1766" alt="frag_old_dis" src="https://github.com/user-attachments/assets/fcc2b776-9364-4ed7-b6c5-3c5331a2689a"; /> New: <img width="3570" height="1766" alt="frag_new_dis" src="https://github.com/user-attachments/assets/a4a35cd2-22e7-4897-96b1-5fb15020fa01"; /> ------------- PR Comment: https://git.openjdk.org/jdk/pull/28934#issuecomment-3917507712
