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

[Jesper Wilhelmsson]

I'm fine with this suggestion.
/Jesper

David Lindholm skrev den 5/3/15 11:26:
> Hi,
>
> Thanks for your input. To me, threads and tasks are different things. A task is
> something a thread can do for a while, but when it is finished with that task it
> can pick something else to do (another task). This view seems to be reflected in
> gcTaskThread.cpp (the thread for running tasks in parallelScavenge). After
> creation, it runs different tasks managed by gcTaskManager. These tasks are
> called names ending with "task".
>
> But I agree that in most cases the word Thread is unnecessary (this was why I
> called the Marker Thread "Marker"). But I don't have anything against using up
> all the 15 chars (we should not shorten the name unnecessarily).
>
> My new suggestion:
>
> "CMS Thread#xxx"
> "CMS Main Thread"
> "G1 Refine#xxx"
> "G1 Marker#xxx"
> "G1 Main Marker"
> "G1 StrDedup#xxx"
> "ParGC Thread#xx"
> "GC Thread#xxx"
>
> This way our threads naming scheme will be aligned with the rest of the JVM. One
> could argue if '#' is necessary. We could leave it out or print '-' instead. The
> CompilerThreads leave them out.
>
>
> Thanks,
> David
>
> On 2015-03-04 16:24, Bengt Rutisson wrote:
>>
>> Hi David and everyone,
>>
>> Naming is the most difficult part of computer science so I doubt that there is
>> an easy answer here. Given that the names are for debugging I guess it is not
>> too important exactly what the names are. More important is that they are
>> unique. I also think that there is really no need to have "thread" in the name
>> since it is pretty obvious that it is a thread.
>>
>> So, my suggestion would be to skip "thread" and to use CamelCase rather than
>> using spaces to save some characters.
>>
>> I don't have strong opinions on this, but here's what I'd suggest:
>>
>> -      _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads",
>> +      _conc_workers = new YieldingFlexibleWorkGang("CMS Threads",
>>
>> "CMSTask"
>>
>>
>>
>> -  set_name("Concurrent Mark-Sweep GC Thread");
>> +  set_name("CMS Main Thread");
>>
>> "CMSMain"
>>
>>
>>
>> -  set_name("G1 Concurrent Refinement Thread#%d", worker_id);
>> +  set_name("G1 ConRefine#%d", worker_id);
>>
>> "G1ConcRefine#%d"
>>
>>
>>
>> -  _parallel_workers = new FlexibleWorkGang("G1 Parallel Marking Threads",
>> +  _parallel_workers = new FlexibleWorkGang("G1 Markers"
>>
>> "G1MarkTask"
>>
>>
>>
>> -  set_name("G1 Main Concurrent Mark GC Thread");
>> +  set_name("G1 Main Marker");
>>
>> "G1ConcMark"
>>
>>
>>
>> -  set_name("String Deduplication Thread");
>> +  set_name("StrDedup Thread");
>>
>> "StringDedup"
>>
>>
>>
>> -  set_name("GC task thread#%d (ParallelGC)", which);
>> +  set_name("ParGC Thread#%d", which);
>>
>> "ParGCTask"
>>
>>
>>
>> -    _workers = new FlexibleWorkGang("Parallel GC Threads", ParallelGCThreads,
>> +    _workers = new FlexibleWorkGang("GC Threads", ParallelGCThreads,
>>
>> "GCParTask"
>>
>>
>> Just my thoughts. And regarding having 3 characters left for the number in the
>> thread name I don't know if that is too important. With the above suggestions
>> this will be possible in most cases but not all. Personally I think that is
>> good enough.
>>
>> Bengt
>>
>>
>> On 2015-03-04 15:11, David Lindholm wrote:
>>> 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
>>>
>>
>