如何计算一个合适的线程池大小参数
原文在这里
下面是一个计算的框架代码:
/** * 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<Runnable> 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<Runnable> 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();}public class MyPoolSizeCalculator extends PoolSizeCalculator { public static void main(String[] args) throws InterruptedException, InstantiationException, IllegalAccessException, ClassNotFoundException { MyThreadSizeCalculator calculator = new MyThreadSizeCalculator(); calculator.calculateBoundaries(new BigDecimal(1.0), new BigDecimal(100000)); } protected long getCurrentThreadCPUTime() { return ManagementFactory.getThreadMXBean().getCurrentThreadCpuTime(); } protected Runnable creatTask() { return new AsynchronousTask(0, "IO", 1000000); } protected BlockingQueue<runnable> createWorkQueue() { return new LinkedBlockingQueue<>(); }}