Adding help information to log tags

[Ioi Lam]

I have filed JDK-8146948: Add help information to log tags

https://bugs.openjdk.java.net/browse/JDK-8146948

- Ioi

On 12/23/15 12:45 PM, Rachel Protacio wrote:
> That seems like a good idea to me! It'd be helpful for the user and 
> also anyone looking at the actual code in logTag.hpp
> Rachel
>
> On 12/23/2015 12:19 AM, Ioi Lam wrote:
>> Now there are a lot of log tags [1], and it looks like many more will 
>> be added. I start to wonder what 'ihop' or 'rt' would do ...
>>
>> Would it make sense to add help information that can be printed to 
>> the user, like
>>
>> #define LOG_TAG_LIST \
>>   LOG_TAG(alloc,      "this prints something about alloc") \
>>   LOG_TAG(age,        "blah blah") \
>>
>> $ java -Xlog:help=alloc
>> alloc - this prints something about alloc
>>
>> $ java -Xlog:help=all
>> alloc - this prints something about alloc
>> age   - blah blah
>>
>>
>> -----------------
>>
>> [1] The list of log tags as of today in jdk9/hs-rt/hotspot
>>
>> #define LOG_TAG_LIST \
>>   LOG_TAG(alloc) \
>>   LOG_TAG(age) \
>>   LOG_TAG(barrier) \
>>   LOG_TAG(bot) \
>>   LOG_TAG(census) \
>>   LOG_TAG(classhisto) \
>>   LOG_TAG(classinit) \
>>   LOG_TAG(comp) \
>>   LOG_TAG(compaction) \
>>   LOG_TAG(cpu) \
>>   LOG_TAG(cset) \
>>   LOG_TAG(defaultmethods) \
>>   LOG_TAG(ergo) \
>>   LOG_TAG(exceptions) \
>>   LOG_TAG(exit) \
>>   LOG_TAG(freelist) \
>>   LOG_TAG(gc) \
>>   LOG_TAG(heap) \
>>   LOG_TAG(humongous) \
>>   LOG_TAG(ihop) \
>>   LOG_TAG(jni) \
>>   LOG_TAG(liveness) \
>>   LOG_TAG(logging) \
>>   LOG_TAG(marking) \
>>   LOG_TAG(metaspace) \
>>   LOG_TAG(monitorinflation) \
>>   LOG_TAG(phases) \
>>   LOG_TAG(plab) \
>>   LOG_TAG(promotion) \
>>   LOG_TAG(ref) \
>>   LOG_TAG(refine) \
>>   LOG_TAG(region) \
>>   LOG_TAG(remset) \
>>   LOG_TAG(rt) \
>>   LOG_TAG(safepoint) \
>>   LOG_TAG(scavenge) \
>>   LOG_TAG(scrub) \
>>   LOG_TAG(start) \
>>   LOG_TAG(state) \
>>   LOG_TAG(stats) \
>>   LOG_TAG(stringdedup) \
>>   LOG_TAG(survivor) \
>>   LOG_TAG(svc) \
>>   LOG_TAG(sweep) \
>>   LOG_TAG(task) \
>>   LOG_TAG(tlab) \
>>   LOG_TAG(time) \
>>   LOG_TAG(verify) \
>>   LOG_TAG(vmoperation)
>>
>>
>