Thread.getState() very slow

[Martin Buchholz]

As a related project, we could fix the JDK so that threads blocked in IO
operations would be much more likely to also report a thread state of
BLOCKED.

Martin

On Fri, Aug 13, 2010 at 09:59, Doug Lea <dl at cs.oswego.edu> wrote:

> Sorry for the long delay on this...
>
>
> On 07/15/10 23:43, Mandy Chung wrote:
>
>> I think making Thread.threadStatus a volatile field and using
>> JVMTI_JAVA_LANG_THREAD_STATE_MASK to convert Thread.threadStatus to
>> Thread.State
>> enum would be a good solution.
>>
>>
>> It'd be great if Doug can do the experiment and evaluate the performance
>> impact.
>> If you want me to prototype the jdk change, let me know and I should be
>> able to
>> make some time to do it next week.
>>
>>
> I did an equivalent experiment (of just directly accessing
> threadState via Unsafe.getIntVolatile and comparing it to
> cached values) and it was about 14X faster.  So anything
> along these lines would be grat. That said, I decided not
> to try to rely on getState in the near term. (Among other
> reasons, it does not usually reflect IO blockage.) So this
> is off the critical path for now. But someday someone is sure
> to run into similar performance issues unless implementation
> is improved.
>
> -Doug
>
>
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