On Tue, 2 Aug 2022 13:34:26 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:
>
> Estimate length
Otherwise looks good to me, thanks
src/java.base/share/classes/java/lang/StackTraceElement.java line 365:
> 363: + methodName.length() + 1
> 364: + Math.max("Unknown Source".length(),
> Objects.requireNonNullElse(fileName, "").length()) + 1
> 365: + Integer.stringSize(lineNumber) + 1;
`Integer.stringSize(lineNumber)` can be further simplify to `11`
-------------
PR: https://git.openjdk.org/jdk/pull/9665
