(RFR)(S)(10): 8176768: hotspot ignores PTHREAD_STACK_MIN when creating new threads

[Chris Plummer]

On 3/15/17 10:23 PM, David Holmes wrote:
> Hi Chris,
>
> On 16/03/2017 3:03 PM, Chris Plummer wrote:
>> Hello,
>>
>> Please review the following:
>>
>> https://bugs.openjdk.java.net/browse/JDK-8176768
>> http://cr.openjdk.java.net/~cjplummer/8176768/webrev.00/webrev.hotspot
>
> Change looks good.
>
>> While working on 8175342 I noticed our stack size on xgene was 8mb even
>> though I was specifying -Xss72k. It turns out the following code was
>> failing:
>>
>>       pthread_attr_setstacksize(&attr, stack_size);
>
> So these really should be checking return values, at least in debug 
> builds. But we can leave that until we refactor the thread startup 
> code into os_posix.cpp.
I considered adding checks. I wasn't sure if we should abort or just 
print a warning if it failed. What refactoring is planned?

Chris
>
> Thanks,
> David
> -----
>
>> Although we computed a minimum stack size of 72k, so -Xss72k should be
>> fine, pthreads on this platform requires the stack be at least 128k, so
>> it failed the pthread_attr_setstacksize() call. The end result is
>> pthread_attr_setstacksize() had no impact on the thread's stack size,
>> and we ended up with the platform default of 8mb. The fix is to round up
>> the following variables to PTHREAD_STACK_MIN after computing their new
>> values:
>>
>>       _java_thread_min_stack_allowed
>>       _compiler_thread_min_stack_allowed
>>       _vm_internal_thread_min_stack_allowed
>>
>> For solaris, there was an issue using PTHREAD_STACK_MIN. You need to
>> #define _POSIX_C_SOURCE >= 199506L in order to get PTHREAD_STACK_MIN
>> #defined, and this needs to be done before including OS header files. I
>> noticed that on solaris we were using thr_min_stack() elsewhere instead
>> of PTHREAD_STACK_MIN, so I decided to do the same with this fix. Either
>> way is ugly (the #define or using thr_min_stack()).
>>
>> And speaking of the existing use of thr_min_stack(), I deleted it. It
>> was being applied before any adjustments to the stack sizes had been
>> made (rounding and adding red, yellow, and shadow zones). This mean the
>> stack ended up being larger than necessary. With the above fix in place,
>> we are now applying thr_min_stack() after recomputing the minimum stack
>> sizes. If for any reason one of those stack sizes is now too small, the
>> correct fix is to adjust the initial stack sizes, not apply
>> thr_min_stack() to the initial stack sizes. However, it looks like no
>> adjustment is needed. I did something close to our nightly testing on
>> all affect platforms, and no new problems turned up.
>>
>> thanks,
>>
>> Chris