Review request 8153912: StackFrame::getFileName and StackFrame::getLineNumber not needed

[Ralph Goers]

Sorry for not getting back sooner but I finally found some time to follow up.

I took a look at https://www.sitepoint.com/deep-dive-into-java-9s-stack-walking-api/ <https://www.sitepoint.com/deep-dive-into-java-9s-stack-walking-api/> and modified the benchmarks that were used there to add a few more use cases. I also created a small set of benchmarks for Java 8 to compare it against.  The resulting project is at https://github.com/rgoers/stackwalker-vs-Reflection_getCallerClass/tree/master/java9 <https://github.com/rgoers/stackwalker-vs-Reflection_getCallerClass/tree/master/java9>.  I’ve summarized the results in https://issues.apache.org/jira/browse/LOG4J2-1359 <https://issues.apache.org/jira/browse/LOG4J2-1359>, but for your convenience here are the bullet points:

1. Walking the Throwable StackTraceElements is significantly faster in Java 8 than Java 9. I am not sure what benchmark Brent used but my results differ.
2. Using StackWalker to get the StackTraceElements in Java 9 is almost twice as slow as walking the Throwable in Java 8. (Log4j relied on this pre-Java9 and apparently will have to continue to do so, but it will now be slower).
3. Using StackWalker to search for the caller's class is about twice as slow as sun.reflect.Reflection.getCallerClass() was (Log4j requires this and it is going to hurt performance).
4. sun.reflect.Reflection.getCallerClass is about 10 times faster than using StackWalker.getCallerClass to obtain the Class object of the immediate caller.
In short it appears that the performance of StackWalker means that we are going to want to avoid using it.

Ralph



> On May 18, 2016, at 11:24 AM, Brent Christian <brent.christian at oracle.com> wrote:
> 
> Hi,
> 
> I compared 8u65 and 9b116 performance on a simple Throwable.getStackTrace() JMH benchmark that I have, using a variety of call stack depths.  Performance looks very similar between the two; if anything, 9b116 has a slight edge for larger stack depths.
> 
> So I don't think the difference is due to the walking of the stack itself, at least based on what I measured.
> 
> HTH,
> -Brent
> 
> On 5/10/16 9:49 AM, Ralph Goers wrote:
>> I just ran one of the Log4j performance tests that specifically captures location information.  To run the test I do
>> 
>> java -jar log4j-perf/target/benchmarks.jar ".*AsyncAppenderLog4j2LocationBenchmark.*" -f 1 -wi 10 -i 20 -t 4 -si true
>> 
>> And the results are:
>> 
>> java version "1.7.0_80
>> 
>> Benchmark                                                             Mode  Samples       Score      Error  Units
>> o.a.l.l.p.j.AsyncAppenderLog4j2LocationBenchmark.throughputSimple    thrpt       20  124819.285 ± 3003.918  ops/s
>> 
>> java version "1.8.0_65"
>> 
>> Benchmark                                                             Mode  Samples       Score      Error  Units
>> o.a.l.l.p.j.AsyncAppenderLog4j2LocationBenchmark.throughputSimple    thrpt       20  123209.746 ± 3064.672  ops/s
>> 
>> 
>> java version "9-ea"
>> Java(TM) SE Runtime Environment (build 9-ea+116)
>> 
>> Benchmark                                                             Mode  Samples      Score      Error  Units
>> o.a.l.l.p.j.AsyncAppenderLog4j2LocationBenchmark.throughputSimple    thrpt       20  96090.261 ± 4565.763  ops/s
>> 
>> 
>> This tells me that Java 9 is about 23% slower than previous versions in walking the stack trace elements.
>> 
>> Ralph
>