I have tested the performance by below code and found the method computeBySTEP in class PackagingDataCalculator spent a lot of time.

public class LogbackTest extends TestCase {
    private static final Logger logger = LoggerFactory.getLogger(LogbackTest.class);

    @Test
    public void test() {
        Profiler.run(new Runnable() {

            @Override
            public void run() {
                logger.error("aaa", new RuntimeException("error"));
            }

        }, 3, 10000, 3).printResult();
    }
}

and here is result:

========================================================================================================================
(unit: milliseconds)
threadNum=3; loops=10000
startTime: 2014-12-30 09:34:18.192
endTime: 2014-12-30 09:34:24.866
totalSpendedTime: 6674

maxMethodTime(run): 79
minMethodTime(run): 0

<method name>, <avg time>, <min time>, <max time>, <0.01% >=>, <0.1% >=>, <1% >=>, <10% >=>, <20% >=>, <50% >=>, <80% >=>, <90% >=>, <99% >=>, <99.9% >=>, <99.99% >=>
run, 0.6434, 0, 79, 62, 16, 16, 0, 0, 0, 0, 0, 0, 0, 0,

========================================================================================================================

by modifying the line in class PackagingDataCalculator:
change:

HashMap<String, ClassPackagingData> cache = new HashMap<String, ClassPackagingData>();

to:

static final HashMap<String, ClassPackagingData> cache = new HashMap<String, ClassPackagingData>();

The performance is improved more than 10 times by the result:
========================================================================================================================
(unit: milliseconds)
threadNum=3; loops=10000
startTime: 2014-12-30 09:33:53.003
endTime: 2014-12-30 09:33:53.41
totalSpendedTime: 407

maxMethodTime(run): 31
minMethodTime(run): 0

<method name>, <avg time>, <min time>, <max time>, <0.01% >=>, <0.1% >=>, <1% >=>, <10% >=>, <20% >=>, <50% >=>, <80% >=>, <90% >=>, <99% >=>, <99.9% >=>, <99.99% >=>
run, 0.0344, 0, 31, 16, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0,

========================================================================================================================