RFR: 8277531: Print actual default stacksize on Windows thread logging

[KIRIYAMA Takuya]

On Fri, 3 Dec 2021 10:01:27 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>>> The problem is that os:;win32::default_stack_size() doesn't necessarily
>>> report the default stack size - it simply reports the stackSize of the
>>> initial main JavaThread thread. So if you print it, it should only be
>>> for JavaThreads that are not CompilerThreads.
>> 
>> In either case of JavaThreads or CompilerThreads,the stack_size argument of _beginthreadex() must be 0 when this code is executed.
>> According to MSDN document, If the stack_size argument can be 0, the operating system uses the same value as the stack that's specified for the main thread.
>> default_stack_size is specified in create_vm() which runs in the main thread, so we use default_stack_size() for CompilerThreads.
>> 
>>> But if you run "java -Xss256k -XX:ThreadStackSize=512K" it will print
>>> 256K as the default stack size when in fact all JavaThreads except the
>>> main thread will get a 512K stack because of ThreadStackSize.
>> 
>> Yes,this behavior is odd. However, this fix executed only if stacksize is not specified.
>> This problem should be fixed in another issue.
>
> Hi, @tkiriyama,
> 
>> > The problem is that os:;win32::default_stack_size() doesn't necessarily
>> > report the default stack size - it simply reports the stackSize of the
>> > initial main JavaThread thread. So if you print it, it should only be
>> > for JavaThreads that are not CompilerThreads.
>> 
>> In either case of JavaThreads or CompilerThreads,the stack_size argument of _beginthreadex() must be 0 when this code is executed. According to MSDN document, If the stack_size argument can be 0, the operating system uses the same value as the stack that's specified for the main thread. default_stack_size is specified in create_vm() which runs in the main thread, so we use default_stack_size() for CompilerThreads.
> 
> Nope, unfortunately not. It runs on the thread invoking CreateJavaVM(). That is usually not the OS main thread (aka primordial thread). In the case of the standard java launcher, the primordial thread spawns a second thread to invoke CreateJavaVM() in, mainly to impose -Xss. In the case of a custom launcher, all bets are open which thread invokes CreateJavaVM(), but typically it's not the primordial thread either. In fact, we have platforms that explicitly forbid invoking CreateJavaVM() on the primordial thread.

Hi, @tstuefe ,

It’s exactly as you said.  
I tried to change _default_stack_size to be set in the main thread or get the stack size of other thread, but it doesn't work well.
I wonder if there might be another way to do this.

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PR: https://git.openjdk.java.net/jdk/pull/6495