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

[Bengt Rutisson]

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
>