RFR: 8073545 - Use shorter and more descriptive names for GC worker threads

[Jesper Wilhelmsson]

Ok, I don't have a strong opinion. I just wanted to highlight these questions to 
make sure there was a conscious decision to go with what you suggests :)

I do think we should try to fit three digit numbers in there though. The whole 
point of this change is to make the names more usable in the debugger.

Thanks,
/Jesper


David Lindholm skrev den 4/3/15 15:11:
> Hi Jesper,
>
> On 2015-03-04 14:52, Jesper Wilhelmsson wrote:
>> Hi David,
>>
>> Thanks for fixing this!
>>
>> A couple of questions:
>>
>> -  set_name("G1 Concurrent Refinement Thread#%d", worker_id);
>> +  set_name("G1 ConRefine#%d", worker_id);
>>
>> Is there any refinement threads that are not concurrent? If not, could we just
>> call this "G1 Refine#%d" to simplify it slightly and remove an implementation
>> detail that doesn't need to be exposed? This would also leave room for three
>> digit numbers in case we have lots of these threads on some systems.
>
> I discussed this with Bengt, and his input was that Concurrent Refinement is a
> well known concept in G1. I have no real opinion here, I'm fine with both
> suggestions.
>
>> -  _parallel_workers = new FlexibleWorkGang("G1 Parallel Marking Threads",
>> +  _parallel_workers = new FlexibleWorkGang("G1 Markers",
>>
>> Markers is cute, but could be misunderstood. Can we call it "G1 Mark Threads"
>> instead?
>
> No, it is too long, the three last character with thread number won't fit (#xx).
>
>> -  set_name("G1 Main Concurrent Mark GC Thread");
>> +  set_name("G1 Main Marker");
>>
>> Again, "Marker" could be misunderstood. I don't have a good replacement though.
>
> I'm open for suggestions, but I think "G1 Main Marker" works.
>
>> -  set_name("GC task thread#%d (ParallelGC)", which);
>> +  set_name("ParGC Thread#%d", which);
>>
>> I don't have a good suggestion for how to make this one character shorter, but
>> currently there is only room for two digit numbers. Maybe just "GC Thread#%d".
>> I don't think these threads will exist at the same time as any other GC
>> threads anyway.
>
> With your suggestion these threads would be called the same thing as the threads
> in sharedHeap. I think it is nice to quickly be able to see that these threads
> indeed belongs to the ParallelGC.
>
>> -  set_name("Gang worker#%d (%s)", id, gang->name());
>> +  set_name("%s#%d", gang->name(), id);
>>
>> Is there any limitation on the length of the name()? If it's too long the
>> number won't show. Can we add an assert to make sure it isn't too long?
>
> I have gone through our current GangWorkers, and they fit. If you want I can add
> an assert for <= 12 characters. OTOH it is not the end of the world if we don't
> see the whole number in the debugger.
>
>
> Thanks,
> David
>
>>
>> Thanks,
>> /Jesper
>>
>>
>> David Lindholm skrev den 4/3/15 13:48:
>>> Hi,
>>>
>>> Please review this small fix which changes the names of the GC threads to be
>>> shorter and more descriptive. There is a limit on 16 characters including the
>>> terminating null byte for this name, since pthread_set_name_np() is used. This
>>> change will make it easier to debug, as these names shows up in the debugger.
>>>
>>> Webrev: http://cr.openjdk.java.net/~brutisso/8073545/webrev.00/
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8073545
>>>
>>> Testing: Passed JPRT.
>>>
>>>
>>> Regards,
>>> David
>