Review request 6983240: guarantee((Solaris::min_stack_allowed >= (StackYellowPages+StackRedPages...) wrong

[Coleen Phillimore]

Can I get one more review?

webrev at http://cr.openjdk.java.net/~coleenp/6983240_2/

Thanks,
Coleen



On 10/05/10 11:26, Coleen Phillimore wrote:
>
> Thanks David - some comments inline...
>
> On 10/04/10 20:41, David Holmes wrote:
>> Hi Coleen,
>>
>> In os_solaris.cpp this comment should now refer to 2*BytesPerWord
> Okay.
>>
>>   // Add in BytesPerWord times page size to account for VM stack during
>>   // class initialization depending on 32 or 64 bit VM.
>>
>> That said this formulation (not your I know) is confusing. What does 
>> bytesPerWord have to do with the amount of stack needed? Is this just 
>> some weird way of getting twice the amount of stack on 64-bit as 
>> 32-bit? Are the pages sizes even the same in that case?
> Yeah, I believe it's just to account for 64 vs. 32 bit.  The page 
> sizes are the same if 32 or 64 bit.  I have
>>
>> Also in os_solaris.cpp isn't this guarantee always false:
>>
>> !   guarantee(os::Solaris::min_stack_allowed >= thr_min_stack(),
>> !             "need to increase min_stack_allowed");
> No, it doesn't assert, because in your next mail you found that 
> thr_min_stack() is smaller than our min_stack_allowed.  I could revert 
> that change but min_stack_allowed() is for the VM to get initialized 
> rather than this thr_min_stack() which is for the OS to initialize the 
> thread.  I would assume the latter is always smaller than the former 
> or something is really wrong.  Changing it back probably doesn't hurt 
> anything.
>
> Thanks,
> Coleen
>>
>> AFAICS min_stack_allowed is set to one of these values:
>>
>> ./os_cpu/solaris_sparc/vm/os_solaris_sparc.cpp:size_t 
>> os::Solaris::min_stack_allowed = 128*K;
>> ./os_cpu/solaris_sparc/vm/os_solaris_sparc.cpp:size_t 
>> os::Solaris::min_stack_allowed = 96*K;
>> ./os_cpu/solaris_x86/vm/os_solaris_x86.cpp:size_t 
>> os::Solaris::min_stack_allowed = 224*K;
>> ./os_cpu/solaris_x86/vm/os_solaris_x86.cpp:size_t 
>> os::Solaris::min_stack_allowed = 64*K;
>>
>> but the manpage for thr_min_stack states:
>>
>>     thr_min_stack() will return the unsigned int  THR_MIN_STACK,
>>     which is the minimum-allowable size for a thread's stack.
>>
>>     In this implementation the default size for a  user-thread's
>>     stack   is   one   mega-byte.
>>
>> 1MB > all the above. ???
>>
>> Cheers,
>> David
>>
>> Coleen Phillimore said the following on 10/05/10 08:45:
>>> Summary: min_stack_allowed is a compile time constant and 
>>> Stack*Pages are settable
>>>
>>> Also stress tested various combinations of -Xss and 
>>> -XX:StackShadowPages=n.  This also fixes a bug
>>> 6346701: stack overflow in native method results in segfault, not a 
>>> StackOverflowError
>>> or rather it fixes the observed SEGVs with different settings of 
>>> -Xss and -XX:StackShadowPages in the evaluation.  We were getting 
>>> stack overflow before the stack overflow exception was initialized, 
>>> causing infinite recusion trying to initialize it.
>>>
>>> Also fixed a random g++ compilation error.
>>>
>>> open webrev at http://cr.openjdk.java.net/~coleenp/6983240/
>>> bug link at http://bugs.sun.com/view_bug.do?bug_id=6983240
>>>
>>> Thanks,
>>> Coleen
>