类型判断(CPU密集orIO密集or混合型)
看应用是CPU密集型的还是IO密集型的，还是混合型的。
CPU密集 CPU密集型的话，一般配置CPU处理器个数+/-1个线程，所谓CPU密集型就是指系统大部分时间是在做程序正常的计算任务，例如数字运算、赋值、分配内存、内存拷贝、循环、查找、排序等，这些处理都需要CPU来完成。
IO密集 IO密集型的话，是指系统大部分时间在跟I/O交互，而这个时间线程不会占用CPU来处理，即在这个时间范围内，可以由其他线程来使用CPU，因而可以多配置一些线程。
混合型 混合型的话，是指两者都占有一定的时间。
IO密集型线程大小
/**
* Support class for thread pool size
*
* @author Nadeem Mohammad
*
*/
public final class ThreadPoolUtil {
private ThreadPoolUtil() {
}
/**
* Each tasks blocks 90% of the time, and works only 10% of its
*lifetime. That is, I/O intensive pool
* @return io intesive Thread pool size
*/
public static int ioIntesivePoolSize() {
double blockingCoefficient = 0.9;
return poolSize(blockingCoefficient);
}
/**
*
* Number of threads = Number of Available Cores / (1 - Blocking
* Coefficient) where the blocking coefficient is between 0 and 1.
*
* A computation-intensive task has a blocking coefficient of 0, whereas an
* IO-intensive task has a value close to 1,
* so we don't have to worry about the value reaching 1.
* @param blockingCoefficient the coefficient
* @return Thread pool size
*/
public static int poolSize(double blockingCoefficient) {
int numberOfCores = Runtime.getRuntime().availableProcessors();
int poolSize = (int) (numberOfCores / (1 - blockingCoefficient));
return poolSize;
}
}
使用
ExecutorService executorService = Executors.newFixedThreadPool(ThreadPoolUtil.ioIntesivePoolSize());
这样语义化设置，表达能力强一些。
doc
