atom feed10 messages in org.apache.commons.userRe: commons pool benchmark issue
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Daniel WuSep 28, 2013 11:50 pm.png
Phil SteitzSep 29, 2013 9:25 am 
Daniel WuSep 29, 2013 6:23 pm 
Phil SteitzSep 29, 2013 7:02 pm 
Daniel WuSep 29, 2013 7:35 pm 
Phil SteitzSep 29, 2013 9:04 pm 
Daniel WuSep 29, 2013 10:29 pm 
Mark ThomasSep 30, 2013 12:27 am 
Daniel WuSep 30, 2013 12:58 am 
James CarmanSep 30, 2013 4:34 am 
Subject:Re: commons pool benchmark issue
From:Phil Steitz (phil@gmail.com)
Date:Sep 29, 2013 9:25:29 am
List:org.apache.commons.user

On 9/28/13 11:50 PM, Daniel Wu wrote:

Hi guys,

I wrote a simple test for commons-pool. The result shows that the performance drops dramatically when concurrent threads increase. e.g, With 50 threads, the throughput is 603326 transactions per second, when threads increase to 600, the throughput drops to 32797. The diagram below is the response time in milliseconds, you can see as the threads increase, the response time grows quickly.

I guess my benchmark test code must have something wrong, could you guys help me review the test code below and figure out what's wrong with my test code?

public class BenchmarkCommons {

public BenchmarkCommons(int workerCount, int loop) throws Exception { double[] statsAvgRespTime = new double[workerCount]; CountDownLatch latch = new CountDownLatch(workerCount);

GenericObjectPool pool = new GenericObjectPool(new PoolableObjectFactory() { @Override public Object makeObject() throws Exception { return new StringBuilder(); } @Override public void destroyObject(Object o) throws Exception { } @Override public boolean validateObject(Object o) { return true; } @Override public void activateObject(Object o) throws Exception { } @Override public void passivateObject(Object o) throws Exception { } }); pool.setMinIdle(25); pool.setMaxIdle(50); pool.setMaxActive(50);

Worker[] workers = new Worker[workerCount]; for (int i = 0; i < workerCount; i++) { workers[i] = new Worker(i, pool, latch, loop, statsAvgRespTime); } long t1 = System.currentTimeMillis(); for (int i = 0; i < workerCount; i++) { workers[i].start(); } latch.await(); long t2 = System.currentTimeMillis(); double stats = 0; for (int i = 0; i < workerCount; i++) { stats += statsAvgRespTime[i]; } System.out.println("Average Response Time:" + new DecimalFormat("0").format(stats / workerCount)); System.out.println("Average Througput Per Second:" + new DecimalFormat("0").format(( (double) loop * workerCount * 1000 ) / (t2 - t1) )); }

private static class Worker extends Thread {

private final int id; private final GenericObjectPool pool; private final CountDownLatch latch; private final int loop; private final double[] statsAvgRespTime;

public Worker(int id, GenericObjectPool pool, CountDownLatch latch, int loop, double[] statsAvgRespTime) { this.id = id; this.pool = pool; this.latch = latch; this.loop = loop; this.statsAvgRespTime = statsAvgRespTime; }

@Override public void run() { long t1 = System.currentTimeMillis(); for (int i = 0; i < loop; i++) { StringBuilder obj = null; try { obj = (StringBuilder) pool.borrowObject(); obj.append("x"); } catch (Exception e) { e.printStackTrace(); } finally { if (obj != null) { try { pool.returnObject(obj); } catch (Exception e) { e.printStackTrace(); } } } } long t2 = System.currentTimeMillis(); statsAvgRespTime[id] = ((double) (t2 - t1)) / loop; latch.countDown(); } }

public static void main(String[] args) throws Exception { System.out.println("-----------warm up------------"); new BenchmarkCommons(50, 100); System.out.println("------------Apache commons pool test-----------"); new BenchmarkCommons(50, 500000); new BenchmarkCommons(100, 500000); new BenchmarkCommons(150, 300000); new BenchmarkCommons(200, 300000); new BenchmarkCommons(250, 100000); new BenchmarkCommons(300, 100000); new BenchmarkCommons(350, 50000); new BenchmarkCommons(400, 50000); new BenchmarkCommons(450, 20000); new BenchmarkCommons(500, 20000); new BenchmarkCommons(550, 10000); new BenchmarkCommons(600, 10000); }

}

First some questions, then some observations.

0) What version of Commons Pool are you running? 1) How many physical CPU cores does the machine you are using to run the test have?

Now some observations:

2) To measure the performance of the pool itself, you should time the borrows and returns, not the full loop including the client action 3) With a large number of threads, the StringBuilders are going to start to get big. You could be running into delays managing these buffers.

If the answer to 1) above is only a few, you could be running into thread scheduling delays. That together with churn caused by 3) could be the main effect. To rule out 1), you could do a test just assigning singleton buffers to each thread, effectively eliminating the pool altogether. I would wager that with a small number of cores you will see degraded performance fairly quickly. To rule out 3), either replace the buffer append with a no-op or use a sleep instead. To more accurately measure pool performance, per 2), time just the pool borrow / returns.

Phil

Regards,

Daniel Wu