RFR(S/M): 8191789 - migrate more Thread-SMR stuff from thread.[ch]pp -> threadSMR.[ch]pp

Tue Dec 5 16:47:55 UTC 2017

On 12/5/17 11:22 AM, Stefan Karlsson wrote:
> Hi Dan,
>
> On 2017-12-05 16:27, Daniel D. Daugherty wrote:
>> Stefan,
>>
>> Thanks for the fast review!
>>
>> Replies embedded below...
>>
>> On 12/5/17 10:07 AM, Stefan Karlsson wrote:
>>> On 2017-12-04 21:22, Daniel D. Daugherty wrote:
>>>> Greetings,
>>>>
>>>> In terms of actual "new/changed" code, this is a "S" review. However,
>>>> because of code motion, the changed/insert/delete counts are the size
>>>> of an "M" or "L" review.
>>>>
>>>> Stefan K, this is one of your Thread-SMR follow-up suggestions so I 
>>>> need
>>>> to hear from you on this thread. Thanks!
>>>
>>> Seems like a good step to me.
>>
>> Thanks! We discussed this during the Thread-SMR project, but didn't
>> do it before going out for OpenJDK review. It was your comment that
>> motivated us to finally do it... :-)
>>
>>
>>> ======================================================================== 
>>>
>>> http://cr.openjdk.java.net/~dcubed/8191789-webrev/jdk10-0/src/hotspot/share/runtime/threadSMR.hpp.udiff.html 
>>>
>>>
>>> Now that you have moved all these functions and variables to a class 
>>> named ThreadsSMRSupport maybe you want to consider getting rid of 
>>> the redundant _smr_ prefix/infix?
>>
>> I thought about that, but it made the sanity checking phase much more
>> difficult because of the noise level in the diffs. What I could do is
>> make that change as the last patch before qfold and qfinish...
>>
>
> It makes sense to me to not change it while moving the files. I think 
> its better to push that change as a separate RFE.

Okay. I'll take it on as a separate changeset.

>
>>
>>> Preexisting: I think you missed moving this in your previous cleanup:
>>>
>>> +  static bool is_a_protected_JavaThread_with_lock(JavaThread 
>>> *thread) {
>>> +    MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : 
>>> Threads_lock);
>>> +    return is_a_protected_JavaThread(thread);
>>> +  }
>>
>> Sorry, I don't know what you mean here. 
>> is_a_protected_JavaThread_with_lock()
>> was in the Threads class and now is in the ThreadsSMRSupport class... 
>> What
>> kind of move did I miss?
>
> I should have been more clear. This function should preferably move 
> out from the header file into an .inline.hpp or .cpp file. During 
> pre-reviews of the SMR work we discussed this, but it seems like we 
> missed this function. This can be handled by a separate RFE.

Since that one wasn't tagged as "inline" so I didn't move it earlier;
my focus in that review cycle was moving inlines out of .hpp files.
I can move it now (and will likely make it an inline)...

>
>>
>>
>>> ======================================================================== 
>>>
>>> http://cr.openjdk.java.net/~dcubed/8191789-webrev/jdk10-0/src/hotspot/share/runtime/thread.cpp.frames.html 
>>>
>>>
>>> Would it make sense to move the following code sections into 
>>> functions in ThreadsSMRSupport? That way we could minimize the 
>>> number of public functions exposed from ThreadSMRSupport.
>>>
>>> ---
>>> 4369   // Maintain fast thread list
>>> 4370   ThreadsList *new_list = 
>>> ThreadsList::add_thread(ThreadsSMRSupport::get_smr_java_thread_list(), 
>>> p);
>>> 4371   if (EnableThreadSMRStatistics) {
>>> 4372 ThreadsSMRSupport::inc_smr_java_thread_list_alloc_cnt();
>>> 4373 
>>> ThreadsSMRSupport::update_smr_java_thread_list_max(new_list->length());
>>> 4374   }
>>> 4375   // Initial _smr_java_thread_list will not generate a 
>>> "Threads::add" mesg.
>>> 4376   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::add: 
>>> new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), 
>>> p2i(new_list));
>>> 4377
>>> 4378   ThreadsList *old_list = 
>>> ThreadsSMRSupport::xchg_smr_java_thread_list(new_list);
>>> 4379   ThreadsSMRSupport::smr_free_list(old_list);
>>
>> Sure. We could refactor this into ThreadsSMRSupport::add_thread()...
>>
>>
>>> ---
>>> 4396     // Maintain fast thread list
>>> 4397     ThreadsList *new_list = 
>>> ThreadsList::remove_thread(ThreadsSMRSupport::get_smr_java_thread_list(), 
>>> p);
>>> 4398     if (EnableThreadSMRStatistics) {
>>> 4399 ThreadsSMRSupport::inc_smr_java_thread_list_alloc_cnt();
>>> 4400       // This list is smaller so no need to check for a 
>>> "longest" update.
>>> 4401     }
>>> 4402
>>> 4403     // Final _smr_java_thread_list will not generate a 
>>> "Threads::remove" mesg.
>>> 4404     log_debug(thread, smr)("tid=" UINTX_FORMAT ": 
>>> Threads::remove: new ThreadsList=" INTPTR_FORMAT, 
>>> os::current_thread_id(), p2i(new_list));
>>> 4405
>>> 4406     ThreadsList *old_list = 
>>> ThreadsSMRSupport::xchg_smr_java_thread_list(new_list);
>>> 4407     ThreadsSMRSupport::smr_free_list(old_list);
>>
>> And we could refactor this into ThreadsSMRSupport::remove_thread()...
>>
>> That would lighten the Thread-SMR footprint in thread.cpp even more...
>
> Sounds good to me.

Thanks.

Dan

>
> Thanks,
> StefanK
>
>>
>> Dan
>>
>>
>>>
>>> Thanks,
>>> StefanK
>>>
>>>>
>>>> I have a simple (but tedious) cleanup fix for Thread-SMR. The bug is:
>>>>
>>>>      JDK-8191789 migrate more Thread-SMR stuff from thread.[ch]pp 
>>>> -> threadSMR.[ch]pp
>>>>      https://bugs.openjdk.java.net/browse/JDK-8191789
>>>>
>>>> This fix is mostly code motion:
>>>>
>>>> - move Thread-SMR related code from thread.cpp -> threadSMR.cpp and
>>>>    from thread.hpp -> threadSMR.hpp
>>>>    - move Threads::_smr_* fields -> ThreadsSMRSupport class
>>>>    - move Thread-SMR functions from Threads -> ThreadsSMRSupport class
>>>>    - move Thread-SMR helper classes from thread.cpp -> threadsSMR.cpp
>>>>    - rename a bunch of Threads::foo() calls -> 
>>>> ThreadsSMRSupport::foo()
>>>>
>>>> - collateral changes:
>>>>    - DO_JAVA_THREADS macro usage by code moved to threadSMR.cpp have
>>>>      to switch to JavaThreadIterator or some other function.
>>>>    - Add ThreadsSMRSupport::inc_smr_java_thread_list_alloc_cnt().
>>>>    - Add ThreadsSMRSupport::update_smr_java_thread_list_max().
>>>>    - Cleanup "friends" for Thread class and ThreadsList class.
>>>>    - Add includes of runtime/threadSMR.hpp in a few files.
>>>>
>>>>
>>>> Here is the webrev URL:
>>>>
>>>> http://cr.openjdk.java.net/~dcubed/8191789-webrev/jdk10-0
>>>>
>>>> This fix was (over) tested with a Mach5 tier[1-5] run. There were no
>>>> unexpected test failures.
>>>>
>>>> These changes were sanity checked a couple of ways:
>>>>
>>>> - Compare pre-Thread-SMR thread.[ch]pp with thread.[ch]pp after 
>>>> this fix
>>>>    - Make sure that remaining Thread-SMR changes in thread.cpp and
>>>>      thread.hpp make sense to leave behind.
>>>>    - Similar comparison for thread.inline.hpp.
>>>> - Compare code removed from thread.cpp with code added to 
>>>> threadSMR.cpp,
>>>>    compare code removed from thread.hpp with code added to 
>>>> threadSMR.hpp,
>>>>    compare code removed from thread.inline.hpp with code added to
>>>>    threadSMR.inline.hpp:
>>>>    - Make sure the deltas make sense.
>>>>
>>>> Thanks, in advance, for any comments, questions or suggestions.
>>>>
>>>> Dan
>>