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

[Daniel Fuchs]

Hi Ralph,

On 13/03/2017 04:25, Ralph Goers wrote:
> 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

StackWalker can give you some performance improvements if
you walk the stack from i=0 to i=StackTraceElements[].length,
and stop somewhere before reaching the end.

If you attempt to walk the stack backwards, starting from
i=StackTraceElements[].length and decreasing i, then I would
not expect as much improvement as you will need to walk the
whole stack anyway.

best regards,

-- daniel

>
>
>
>> 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
>>
>