On Fri, 21 Nov 2025 16:54:48 GMT, Trevor Bond <[email protected]> wrote:
> Enhance `ResourceParsingClassHierarchyResolver.getClassInfo` to use > `ClassReaderImpl` to improve performance. Previously this method inflated and > stored all UTF-8 entries in the constant pool and later accessed the array of > strings to try finding the name of the superclass. `ClassReaderImpl` instead > stores constant pool offsets and later lazily reads/inflates UTF8 entries as > needed. > > I’ve ran all tier 1 tests and tests within `test/jdk/jdk/classfile` on the > latest version of this change, and they all pass. > > I ran some informal performance testing to see if these changes led to any > improvement. I created a .class file with several thousand unique strings in > a String array to deliberately enlarge the number of UTF-8 entries in the > constant pool. I then benchmarked the performance of running a process nearly > identical to `ClassHierarchyInfoTest.testClassLoaderParsingResolver` on this > custom class over 200 runs using JMH. The results are as follows. > > | Version | Avg Time (ns/op) | Δ vs Before | > |--------|------------------:|-------------| > | **Before** | 1,483,671.539 ± 3,477.744 | — | > | **After** | 1,380,064.517 ± 3,482.434 | ≈ 7.0% faster | It might be better to make the previous version lazy, as the new version requires pre‑parsing the whole input, whereas the old version would only read the classfile header. ------------- PR Comment: https://git.openjdk.org/jdk/pull/28458#issuecomment-3566366203
