On Mon, 1 Aug 2022 17:35:05 GMT, David Schlosnagle <d...@openjdk.org> wrote:
>> I would like to contribute an optimized version of >> `StackTraceElement#toString()` that uses a single StringBuilder throughout >> creation to avoid intermediate `String` allocations. >> `StackTraceElement#toString()` is used in a number of JDK code paths >> including `Throwable#printStackTrace()`, as well as many JDK consumers may >> transform `StackTraceElement` `toString()` in logging frameworks capturing >> throwables and exceptions, and diagnostics performing dumps. >> >> Given this usage and some observed JFR profiles from production services, >> I'd like to reduce the intermediate allocations to reduce CPU pressure in >> these circumstances. I have added a couple benchmarks for a sample >> `Throwable#printStackTrace()` converted to String via `StringWriter` and >> individual `StackTraceElement` `toString`. The former shows ~15% >> improvement, while the latter shows ~40% improvement. >> >> Before >> >> Benchmark Mode Cnt Score Error >> Units >> StackTraceElementBench.printStackTrace avgt 15 167147.066 ± 4260.521 >> ns/op >> StackTraceElementBench.toString avgt 15 132.781 ± 2.095 >> ns/op >> >> >> After >> >> Benchmark Mode Cnt Score Error >> Units >> StackTraceElementBench.printStackTrace avgt 15 142909.133 ± 2290.720 >> ns/op >> StackTraceElementBench.toString avgt 15 78.939 ± 0.469 >> ns/op > > David Schlosnagle has updated the pull request incrementally with one > additional commit since the last revision: > > Address comments Since constructing a `String` from a `StringBuilder` requires an array copy anyway, you don't need to be exact in the capacity of the builder and overshooting is fine. This can simplify the length calculation a lot. Thanks. ------------- PR: https://git.openjdk.org/jdk/pull/9665
