-Xss和-XX有什么区别：ThreadStackSize？ [英] What is the difference between -Xss and -XX:ThreadStackSize?

问题描述

我只想控制Java（groovy）应用程序中所有线程的堆栈大小。对于Hotspot Oracle VM，我知道有两个参数可以做到这一点（ -Xss 和 XX：ThreadStackSize ）。

I just want to control the stack size for all of my threads in a Java (groovy) application. For the Hotspot Oracle VM, I know that there are two parameters doing that (-Xss and XX:ThreadStackSize).

哪个是首选？它们之间有什么区别吗？关于Open JDK 7 有人在邮件列表中询问，声明 -Xss 对于Hotpot VM来说与 -XX：ThreadStackSize 相同。

Which is the preferred one? Is there any difference between them? Regarding Open JDK 7 someone asked on the mailing list, stating that -Xss is the same for the Hotpot VM as -XX:ThreadStackSize.

关键是，我正在测量可以在我的系统上启动多少个线程。
我的groovy脚本就是这样的：

The point is, that I am measuring how many threads can be started on my system. My groovy script which does this looks like:

int count = 0

def printCountThreads = {
     println("XXX There were started $count threads.")
}

try {
    while(true){
            new Thread({Thread.sleep(Integer.MAX_VALUE)}).start()
            count++
            if(count % 1000 == 0){
                    printCountThreads()
            }
    }
} catch (Throwable e){
    printCountThreads()
    throw e
}

有趣的是，我只使用 - XX：ThreadStackSize 获得减少的线程数。我正在使用环境变量JAVA_OPTS中的不同内容启动groovy应用程序。

Interestingly enough I just get a reduced number of of threads using -XX:ThreadStackSize. I am starting the groovy application with and with different content in the environment variable JAVA_OPTS.

groovy countmax-threads.groovy

当我将JAVA_OPTS设置为 -XX：ThreadStackSize = 2m 时，我会获得大约1000个启动的线程，直到消耗内存为止。但是，当我使用 JAVA_OPTS =' - Xss2m'时，我会得到大约32000个线程，直到出现预期的错误。所以似乎 -Xss 根本不起作用。

When I set JAVA_OPTS to -XX:ThreadStackSize=2m, I get about 1000 started threads until the memory is consumed. But, when I use JAVA_OPTS='-Xss2m', I get about 32000 threads until the expected error arises. So it seems that -Xss does not work at all.

我正在使用

java version1.8.0_05

Java（TM）SE运行时环境（版本1.8.0_05-b13）

Java HotSpot（TM）64位服务器VM（版本25.5-b02，混合模式）

java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)

在具有四个硬件线程和大约8 GB RAM的Ubuntu 14.04 64位计算机上。

on a Ubuntu 14.04 64 bit machine with four hardware threads and about 8 GB of RAM.

更新：

我在Windows 7 64位机器和另一台JDK上重新验证了这一点：

I reverified this on my Windows 7 64 bit machine and another JDK:

java版1.8.0_20
Java（TM）SE运行时环境（版本1.8.0_20-b26）
Java HotSpot（TM）64位服务器VM（版本25.20-b23，混合模式）

java version "1.8.0_20" Java(TM) SE Runtime Environment (build 1.8.0_20-b26) Java HotSpot(TM) 64-Bit Server VM (build 25.20-b23, mixed mode)

并且 -Xss 和 -XX：ThreadStackSize 按预期工作（正如一些答案所指出的那样）。所以我认为这是一个特定于Linux的问题，甚至是JDK版本1.8.05中的一个错误。

and there -Xss and -XX:ThreadStackSize work as expected (as some answers pointed out). So I suppose it is a Linux specific problem or even a bug in the JDK version 1.8.05.

推荐答案

-Xss 是Java HotSpot VM识别的标准选项。

-Xss is standard options recognized by the Java HotSpot VM.

-XX：ThreadStackSize 其他 -XX 期权不稳定，如有更改，恕不另行通知。

-XX:ThreadStackSize as other -XX options are not stable and are subject to change without notice.

参见 Java HotSpot VM选项

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