Performance improvement when gathering Location Information

When gathering Location Information in Log4jLogEvent
Log4j uses Thread.currentThread().getStackTrace()

Using (new Throwable()).getStackTrace(); would be more performant especially for larger stacks according to various benchmarks:

• http://alexradzin.blogspot.co.at/2011/12/how-slow-getstacktrace-is.html
• http://stackoverflow.com/questions/2347828/how-expensive-is-thread-getstacktrace

This can easily be verified with a simple JMH Benchmark test.

What would help in addition is to skip the Log4j Part when iterating over the StackTrace - use i=4 or whatever you may consider as being save enough instead of starting with i=0.

Basically something like:

final StackTraceElement[] stackTrace = (new Throwable()).getStackTrace();
for (int i = 4; i < stackTrace.length; i++) {
}