分配的Java堆栈在哪里？ [英] where is the Java stack allocated?
问题描述
我在网站上注意到以下内容：JVM HotSpot内存分为3个内存空间：
I have noted the following from a website: The JVM HotSpot memory is split between 3 memory spaces:
- Java堆
- PermGen（永久代）空间
- 原生堆（C-Heap）
在hotSpot JVM中分配的堆栈在哪里？在本机堆中？
Where is the stack allocated in hotSpot JVM? In native heap?
更新：
另一个参考信息：
对于64位VM，C-Heap容量=物理服务器总RAM &安培;虚拟内存 - Java堆 - PermGen
update: another reference info: For a 64-bit VM, the C-Heap capacity = Physical server total RAM & virtual memory – Java Heap - PermGen
推荐答案
答案是：
-
这是依赖于实现的。
It is implementation dependent.
在我看到的实现中，线程堆栈分配由标准处理C本机线程库，它看起来像是要去操作系统为堆栈分配一个内存段。所以以上都不是。
In the implementation I looked at, the thread stack allocation was handled by the standard C native thread library, and it looked like the library was going to the OS to allocate a memory segment for the stack. So "none of the above".
您可以通过深入研究与您的平台相关的OpenJDK源代码来确认这一点。
You can confirm this by delving into the OpenJDK source code relevant to your platform.
更新
从旧问题来看，这是来自 pthread_create 的代码片段，用于请求分配线程堆栈。此方法由JVM线程实现使用来创建本机线程。
From an old question, here is the snippet of code from pthread_create that requests the allocation of the thread stack. This method used by the JVM thread implementation to create the native thread.
mmap(0, attr.__stacksize,
PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
如您所见，它只是使用 mmap 系统调用来从操作系统请求内存段。正如我在评论中所说，这不是常规Java堆，不是Permgen堆，也不是C本机堆。它是操作系统特别请求的一段内存。
As you can see, it just uses the mmap system call to request a memory segment from the operating system. As I said in a comment, this is NOT the regular Java heap, NOT the Permgen heap, and NOT the C native heap. It is a segment of memory specifically requested from the operating system.
作为参考，这里是 mmap系统调用手册输入。
更新：另一个参考信息：对于64位VM，C-Heap容量=物理服务器总RAM&虚拟内存 - Java堆 - PermGen
update: another reference info: For a 64-bit VM, the C-Heap capacity = Physical server total RAM & virtual memory – Java Heap - PermGen
IMO，这是一个过于简单化的过程。 （并且请提供您在何处找到此信息的链接...以便我们可以以原始形式阅读。）
IMO, that is an oversimplification. (And please provide a link to where you found this information ... so that we can read it in its original form.)
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