On Mon, 1 Aug 2022 17:08:12 GMT, Сергей Цыпанов <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
>
> src/java.base/share/classes/java/lang/StackTraceElement.java line 366:
>
>> 364: if (!dropClassLoaderName() && classLoaderName != null &&
>> !classLoaderName.isEmpty()) {
>> 365: prefixClassLoader = true;
>> 366: length += classLoaderName.length() + 1 /* '/' */;
>
> Do we still need this comment `/* '/' */`?
happy to remove these if desired
> src/java.base/share/classes/java/lang/StackTraceElement.java line 400:
>
>> 398: dest.append(fileName)
>> 399: .append(':')
>> 400: .append(Integer.toString(lineNumber))
>
> I think `Integer.toString(lineNumber)` is redundant here, you can pass `int`
> directly
`Appendable` does not currently have an `append(int)` method on the interface,
though `StringBuilder` does. We could add it to `Appendable` via default method
if so desired:
default Appendable append(int value) {
return append(Integer.toString(value));
}
-------------
PR: https://git.openjdk.org/jdk/pull/9665
