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

[David Lindholm]

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