如何合理地估算线程池大小？

package threadpool;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.BlockingQueue;
/**
 * A class that calculates the optimal thread pool boundaries. It takes the
 * desired target utilization and the desired work queue memory consumption as
 * input and retuns thread count and work queue capacity.
 *
 * @author Niklas Schlimm
 */
public abstract class PoolSizeCalculator {
    /**
     * The sample queue size to calculate the size of a single {@link Runnable}
     * element.
     */
    private final int SAMPLE_QUEUE_SIZE = 1000;
    /**
     * Accuracy of test run. It must finish within 20ms of the testTime
     * otherwise we retry the test. This could be configurable.
     */
    private final int EPSYLON = 20;
    /**
     * Control variable for the CPU time investigation.
     */
    private volatile boolean expired;
    /**
     * Time (millis) of the test run in the CPU time calculation.
     */
    private final long testtime = 3000;
    /**
     * Calculates the boundaries of a thread pool for a given {@link Runnable}.
     *
     * @param targetUtilization the desired utilization of the CPUs (0 <= targetUtilization <=      *            1)      * @param targetQueueSizeBytes      *            the desired maximum work queue size of the thread pool (bytes)
     */
    protected void calculateBoundaries(BigDecimal targetUtilization, BigDecimal targetQueueSizeBytes) {
        calculateOptimalCapacity(targetQueueSizeBytes);
        Runnable task = creatTask();
        start(task);
        start(task); // warm up phase
        long cputime = getCurrentThreadCPUTime();
        start(task); // test intervall
        cputime = getCurrentThreadCPUTime() - cputime;
        long waittime = (testtime * 1000000) - cputime;
        calculateOptimalThreadCount(cputime, waittime, targetUtilization);
    }
    private void calculateOptimalCapacity(BigDecimal targetQueueSizeBytes) {
        long mem = calculateMemoryUsage();
        BigDecimal queueCapacity = targetQueueSizeBytes.divide(new BigDecimal(mem),
                RoundingMode.HALF_UP);
        System.out.println("Target queue memory usage (bytes): "
                + targetQueueSizeBytes);
        System.out.println("createTask() produced " + creatTask().getClass().getName() + " which took " + mem + " bytes in a queue");
        System.out.println("Formula: " + targetQueueSizeBytes + " / " + mem);
        System.out.println("* Recommended queue capacity (bytes): " + queueCapacity);
    }
    /**
     * Brian Goetz' optimal thread count formula, see 'Java Concurrency in
     * * Practice' (chapter 8.2)      *
     * * @param cpu
     * *            cpu time consumed by considered task
     * * @param wait
     * *            wait time of considered task
     * * @param targetUtilization
     * *            target utilization of the system
     */
    private void calculateOptimalThreadCount(long cpu, long wait,
                                             BigDecimal targetUtilization) {
        BigDecimal waitTime = new BigDecimal(wait);
        BigDecimal computeTime = new BigDecimal(cpu);
        BigDecimal numberOfCPU = new BigDecimal(Runtime.getRuntime()
                .availableProcessors());
        BigDecimal optimalthreadcount = numberOfCPU.multiply(targetUtilization)
                .multiply(new BigDecimal(1).add(waitTime.divide(computeTime,
                        RoundingMode.HALF_UP)));
        System.out.println("Number of CPU: " + numberOfCPU);
        System.out.println("Target utilization: " + targetUtilization);
        System.out.println("Elapsed time (nanos): " + (testtime * 1000000));
        System.out.println("Compute time (nanos): " + cpu);
        System.out.println("Wait time (nanos): " + wait);
        System.out.println("Formula: " + numberOfCPU + " * "
                + targetUtilization + " * (1 + " + waitTime + " / "
                + computeTime + ")");
        System.out.println("* Optimal thread count: " + optimalthreadcount);
    }
    /**
     * * Runs the {@link Runnable} over a period defined in {@link #testtime}.
     * * Based on Heinz Kabbutz' ideas
     * * (http://www.javaspecialists.eu/archive/Issue124.html).
     * *
     * * @param task
     * *            the runnable under investigation
     */
    public void start(Runnable task) {
        long start = 0;
        int runs = 0;
        do {
            if (++runs > 5) {
                throw new IllegalStateException("Test not accurate");
            }
            expired = false;
            start = System.currentTimeMillis();
            Timer timer = new Timer();
            timer.schedule(new TimerTask() {
                public void run() {
                    expired = true;
                }
            }, testtime);
            while (!expired) {
                task.run();
            }
            start = System.currentTimeMillis() - start;
            timer.cancel();
        } while (Math.abs(start - testtime) > EPSYLON);
        collectGarbage(3);
    }
    private void collectGarbage(int times) {
        for (int i = 0; i < times; i++) {
            System.gc();
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                break;
            }
        }
    }
    /**
     * Calculates the memory usage of a single element in a work queue. Based on
     * Heinz Kabbutz' ideas
     * (http://www.javaspecialists.eu/archive/Issue029.html).
     *
     * @return memory usage of a single {@link Runnable} element in the thread
     * pools work queue
     */
    public long calculateMemoryUsage() {
        BlockingQueue queue = createWorkQueue();
        for (int i = 0; i < SAMPLE_QUEUE_SIZE; i++) {
            queue.add(creatTask());
        }
        long mem0 = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
        long mem1 = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
        queue = null;
        collectGarbage(15);
        mem0 = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
        queue = createWorkQueue();
        for (int i = 0; i < SAMPLE_QUEUE_SIZE; i++) {
            queue.add(creatTask());
        }
        collectGarbage(15);
        mem1 = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
        return (mem1 - mem0) / SAMPLE_QUEUE_SIZE;
    }
    /**
     * Create your runnable task here.
     *
     * @return an instance of your runnable task under investigation
     */
    protected abstract Runnable creatTask();
    /**
     * Return an instance of the queue used in the thread pool.
     *
     * @return queue instance
     */
    protected abstract BlockingQueue createWorkQueue();
    /**
     * Calculate current cpu time. Various frameworks may be used here,
     * depending on the operating system in use. (e.g.
     * http://www.hyperic.com/products/sigar). The more accurate the CPU time
     * measurement, the more accurate the results for thread count boundaries.
     *
     * @return current cpu time of current thread
     */
    protected abstract long getCurrentThreadCPUTime();
}

package threadpool;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.management.ManagementFactory;
import java.math.BigDecimal;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
public class SimplePoolSizeCaculatorImpl extends PoolSizeCalculator {
    @Override
    protected Runnable creatTask() {
        return new AsyncIOTask();
    }
    @Override
    protected BlockingQueue createWorkQueue() {
        return new LinkedBlockingQueue(1000);
    }
    @Override
    protected long getCurrentThreadCPUTime() {
        return ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime();
    }
    public static void main(String[] args) {
        PoolSizeCalculator poolSizeCalculator = new SimplePoolSizeCaculatorImpl();
        poolSizeCalculator.calculateBoundaries(new BigDecimal(1.0), new BigDecimal(100000));
    }
}
/**
 * 自定义的异步IO任务
 * @author Will
 *
 */
class AsyncIOTask implements Runnable {
    public void run() {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        try {
            String getURL = "http://baidu.com";
            URL getUrl = new URL(getURL);
            connection = (HttpURLConnection) getUrl.openConnection();
            connection.connect();
            reader = new BufferedReader(new InputStreamReader(
                    connection.getInputStream()));
            String line;
            while ((line = reader.readLine()) != null) {
                // empty loop
            }
        }
        catch (IOException e) {
        } finally {
            if(reader != null) {
                try {
                    reader.close();
                }
                catch(Exception e) {
                }
            }
            connection.disconnect();
        }
    }
}

Target queue memory usage (bytes): 100000
createTask() produced threadpool.AsyncIOTask which took 40 bytes in a queue
Formula: 100000 / 40
* Recommended queue capacity (bytes): 2500
Number of CPU: 8
Target utilization: 1
Elapsed time (nanos): 3000000000
Compute time (nanos): 280801800
Wait time (nanos): 2719198200
Formula: 8 * 1 * (1 + 2719198200 / 280801800)
* Optimal thread count: 88

ThreadPoolExecutor pool = new ThreadPoolExecutor(88, 88, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(2500));

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  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>threadpool</groupId>
    <artifactId>dark-magic</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>dark_magic</name>
    <url>http://maven.apache.org</url>
    <properties>
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    </properties>
    <dependencies>
    </dependencies>
    <build>
        <finalName>dark-magic</finalName>
        <plugins>
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                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <appendAssemblyId>false</appendAssemblyId>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                    <archive>
                        <manifest>
                            <!-- 此处指定main方法入口的class -->
                            <mainClass>threadpool.SimplePoolSizeCaculatorImpl</mainClass>
                        </manifest>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>assembly</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>