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

[David Lindholm]

Hi,

Thanks. New webrev available at: 
http://cr.openjdk.java.net/~mgerdin/david/8073545/webrev.01/


Regards,
David

On 2015-03-05 14:41, Erik Helin wrote:
> On 2015-03-05, David Lindholm wrote:
>> 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"
> These names looks good to me. I also had a look at the patch and
> noticed:
> -  set_name("GC task thread#%d (ParallelGC)", which);
> +//  set_name("GC task thread#%d (ParallelGC)", which);
>
> Could you please remove the line you commented out?
>
> Thanks,
> Erik
>
>> 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